feat(bookings): add dry_run slot picker with live validation

Implemented complete slot picker flow with real-time validation:

**Components Created:**

1. **SlotPickerTile** (src/components/bookings/SlotPickerTile.tsx)
   - Individual slot tile with dry_run validation
   - 4 validation states: idle, validating, valid, invalid
   - Real-time API calls to validateMoveBooking() on selection
   - Visual feedback: checkmark (✓) for valid, X for invalid, spinner during validation
   - Displays validation errors inline with bullet points
   - Shows success message "✓ Valid - ready to confirm"
   - Integrates CapacityDisplay component
   - Color-coded borders (green=valid, red=invalid, gray=idle)
   - Disabled state for full/cancelled slots
   - onValidationResult callback for parent coordination

2. **SlotPickerModal** (src/components/bookings/SlotPickerModal.tsx)
   - Full-screen modal for slot selection
   - Groups slots by date (weekday, month, day, year)
   - Sorts dates chronologically
   - Filters out current slot
   - 2-column grid layout for slots
   - Info banner with policy hints (14-day window, product-type, club match)
   - Confirm button disabled until valid slot selected
   - Loading states with spinner
   - Empty state with helpful message
   - Tracks validation state from child tiles

3. **CancelBookingModal** (src/components/bookings/CancelBookingModal.tsx)
   - Confirmation modal for booking cancellation
   - Optional reason textarea (500 char limit)
   - Displays grace period policy (reads from booking.policies or defaults to 15 min)
   - Shows booking details (court, time, attendees count)
   - Warning banner: "This action cannot be undone"
   - Policy info banner with grace period details
   - Two-button layout: "Keep Booking" / "Yes, Cancel Booking"
   - Loading state with spinner

**Features:**
- Live dry_run validation on slot selection (no manual trigger needed)
- Real-time feedback with checkmarks/errors
- Graceful error handling (network failures, validation errors)
- Parameterized error messages from getBookingErrorMessage()
- SSR-safe with proper disabled states
- Professional slate theme matching existing UI
- Responsive grid layouts

**Integration:**
- SlotPickerTile calls validateMoveBooking() API automatically
- SlotPickerModal coordinates validation state
- CancelBookingModal reads policy fields from BookingDetail
- All components ready for integration into BookingDrawer

Related: Phase 3, Booking Admin API v1.1, BUILD #23

src/components/bookings/CancelBookingModal.tsx

@@ -0,0 +1,144 @@
+/**
+ * Cancel Booking Modal Component
+ *
+ * Confirmation modal for cancelling bookings with optional reason.
+ * Displays grace period policy information.
+ */
+
+'use client';
+
+import { useState } from 'react';
+import { X, AlertTriangle, Loader2 } from 'lucide-react';
+import type { BookingDetail } from '@/src/types/bookings';
+
+interface CancelBookingModalProps {
+  booking: BookingDetail;
+  onConfirm: (reason?: string) => void;
+  onCancel: () => void;
+  loading?: boolean;
+}
+
+export default function CancelBookingModal({
+  booking,
+  onConfirm,
+  onCancel,
+  loading = false,
+}: CancelBookingModalProps) {
+  const [reason, setReason] = useState('');
+
+  function handleConfirm() {
+    onConfirm(reason.trim() || undefined);
+  }
+
+  // Extract grace period from policies if available
+  const graceMinutes = booking.policies?.cancel_grace_minutes || 15;
+  const graceAnchor = booking.policies?.cancel_grace_anchor || 'start';
+
+  return (
+    <div className="fixed inset-0 bg-black bg-opacity-50 z-50 flex items-center justify-center">
+      <div className="bg-white rounded-2xl p-8 max-w-lg w-full mx-4">
+        {/* Header */}
+        <div className="flex items-center justify-between mb-6">
+          <div className="flex items-center space-x-3">
+            <div className="w-10 h-10 bg-red-100 rounded-full flex items-center justify-center">
+              <AlertTriangle className="w-5 h-5 text-red-600" />
+            </div>
+            <h2 className="text-2xl font-bold text-slate-900">Cancel Booking</h2>
+          </div>
+          <button
+            onClick={onCancel}
+            className="text-slate-400 hover:text-slate-600 transition-colors"
+            disabled={loading}
+          >
+            <X className="w-6 h-6" />
+          </button>
+        </div>
+
+        {/* Warning */}
+        <div className="bg-red-50 border-2 border-red-200 rounded-lg p-4 mb-6">
+          <p className="text-sm text-red-900 font-semibold mb-2">
+            This action cannot be undone
+          </p>
+          <p className="text-sm text-red-700">
+            Cancelling this booking will free up the slot and notify all attendees.
+          </p>
+        </div>
+
+        {/* Grace Period Info */}
+        <div className="bg-blue-50 border-2 border-blue-200 rounded-lg p-4 mb-6">
+          <p className="text-xs font-semibold text-blue-900 uppercase mb-1">Policy</p>
+          <p className="text-sm text-blue-700">
+            Changes allowed until {graceMinutes} minutes after slot{' '}
+            {graceAnchor === 'end' ? 'ends' : 'starts'}
+          </p>
+        </div>
+
+        {/* Booking Details */}
+        <div className="bg-slate-50 border-2 border-slate-200 rounded-lg p-4 mb-6">
+          <p className="text-xs font-semibold text-slate-600 uppercase mb-2">Booking Details</p>
+          <div className="space-y-1">
+            <p className="text-sm text-slate-900">
+              <span className="font-medium">Court:</span> {booking.slot.court.name}
+            </p>
+            <p className="text-sm text-slate-900">
+              <span className="font-medium">Time:</span>{' '}
+              {new Date(booking.slot.starts_at).toLocaleString('en-US', {
+                weekday: 'short',
+                month: 'short',
+                day: 'numeric',
+                hour: 'numeric',
+                minute: '2-digit',
+              })}
+            </p>
+            <p className="text-sm text-slate-900">
+              <span className="font-medium">Attendees:</span> {booking.attendees.length}
+            </p>
+          </div>
+        </div>
+
+        {/* Reason (Optional) */}
+        <div className="mb-6">
+          <label className="block text-sm font-semibold text-slate-900 mb-2">
+            Reason for Cancellation (Optional)
+          </label>
+          <textarea
+            value={reason}
+            onChange={(e) => setReason(e.target.value)}
+            placeholder="E.g., Court maintenance, double booking, player request..."
+            rows={3}
+            maxLength={500}
+            disabled={loading}
+            className="w-full px-4 py-3 border-2 border-slate-200 rounded-lg font-medium focus:border-slate-900 focus:outline-none transition-colors resize-none"
+          />
+          <p className="text-xs text-slate-500 mt-1">{reason.length} / 500 characters</p>
+        </div>
+
+        {/* Actions */}
+        <div className="flex items-center justify-between space-x-3">
+          <button
+            onClick={onCancel}
+            disabled={loading}
+            className="flex-1 px-6 py-3 bg-slate-200 text-slate-700 font-semibold rounded-lg hover:bg-slate-300 transition-colors disabled:opacity-50"
+          >
+            Keep Booking
+          </button>
+
+          <button
+            onClick={handleConfirm}
+            disabled={loading}
+            className="flex-1 px-6 py-3 bg-red-600 text-white font-semibold rounded-lg hover:bg-red-700 transition-colors disabled:opacity-50"
+          >
+            {loading ? (
+              <span className="flex items-center justify-center space-x-2">
+                <Loader2 className="w-4 h-4 animate-spin" />
+                <span>Cancelling...</span>
+              </span>
+            ) : (
+              'Yes, Cancel Booking'
+            )}
+          </button>
+        </div>
+      </div>
+    </div>
+  );
+}

src/components/bookings/SlotPickerModal.tsx

@@ -0,0 +1,177 @@
+/**
+ * Slot Picker Modal Component
+ *
+ * Modal for selecting a new slot when moving a booking.
+ * Provides live dry_run validation with visual feedback.
+ */
+
+'use client';
+
+import { useState } from 'react';
+import { X, Calendar, Loader2 } from 'lucide-react';
+import type { BookingSlot } from '@/src/types/bookings';
+import SlotPickerTile from './SlotPickerTile';
+
+interface SlotPickerModalProps {
+  bookingId: number;
+  currentSlotId: number;
+  availableSlots: Array<
+    Pick<
+      BookingSlot,
+      'slot_instance_id' | 'starts_at' | 'ends_at' | 'capacity' | 'booked_count' | 'capacity_remaining' | 'status'
+    > & {
+      court: {
+        court_id: number;
+        name: string;
+      };
+    }
+  >;
+  onSelect: (slotInstanceId: number) => void;
+  onCancel: () => void;
+  loading?: boolean;
+}
+
+export default function SlotPickerModal({
+  bookingId,
+  currentSlotId,
+  availableSlots,
+  onSelect,
+  onCancel,
+  loading = false,
+}: SlotPickerModalProps) {
+  const [selectedSlotId, setSelectedSlotId] = useState<number | null>(null);
+  const [isValid, setIsValid] = useState(false);
+  const [validationReasons, setValidationReasons] = useState<string[]>([]);
+
+  function handleValidationResult(valid: boolean, reasons?: string[]) {
+    setIsValid(valid);
+    setValidationReasons(reasons || []);
+  }
+
+  function handleConfirm() {
+    if (selectedSlotId && isValid) {
+      onSelect(selectedSlotId);
+    }
+  }
+
+  // Filter out current slot and group by date
+  const slotsToShow = availableSlots.filter(
+    (slot) => slot.slot_instance_id !== currentSlotId
+  );
+
+  // Group slots by date
+  const slotsByDate = slotsToShow.reduce((acc, slot) => {
+    const date = new Date(slot.starts_at).toLocaleDateString('en-US', {
+      weekday: 'long',
+      month: 'long',
+      day: 'numeric',
+      year: 'numeric',
+    });
+
+    if (!acc[date]) {
+      acc[date] = [];
+    }
+    acc[date].push(slot);
+    return acc;
+  }, {} as Record<string, typeof slotsToShow>);
+
+  // Sort dates
+  const sortedDates = Object.keys(slotsByDate).sort((a, b) => {
+    return new Date(a).getTime() - new Date(b).getTime();
+  });
+
+  return (
+    <div className="fixed inset-0 bg-black bg-opacity-50 z-50 flex items-center justify-center">
+      <div className="bg-white rounded-2xl p-8 max-w-4xl w-full mx-4 max-h-[90vh] overflow-y-auto">
+        {/* Header */}
+        <div className="flex items-center justify-between mb-6">
+          <div className="flex items-center space-x-3">
+            <Calendar className="w-6 h-6 text-slate-900" />
+            <h2 className="text-2xl font-bold text-slate-900">Select New Slot</h2>
+          </div>
+          <button
+            onClick={onCancel}
+            className="text-slate-400 hover:text-slate-600 transition-colors"
+            disabled={loading}
+          >
+            <X className="w-6 h-6" />
+          </button>
+        </div>
+
+        {/* Info Banner */}
+        <div className="bg-blue-50 border-2 border-blue-200 rounded-lg p-4 mb-6">
+          <p className="text-sm text-blue-900">
+            <span className="font-semibold">Select a slot below.</span> We'll validate it in
+            real-time and show you if it's available for this booking.
+          </p>
+          <p className="text-xs text-blue-700 mt-2">
+            Move window: 14 days · Product type must match · Club must match
+          </p>
+        </div>
+
+        {/* Slots Grid */}
+        {loading ? (
+          <div className="flex items-center justify-center py-12">
+            <Loader2 className="w-8 h-8 text-slate-600 animate-spin" />
+          </div>
+        ) : slotsToShow.length === 0 ? (
+          <div className="bg-slate-50 border-2 border-slate-200 rounded-lg p-12 text-center">
+            <Calendar className="w-12 h-12 text-slate-400 mx-auto mb-4" />
+            <p className="text-slate-600">No available slots found</p>
+            <p className="text-sm text-slate-500 mt-2">
+              Try adjusting your filters or check back later
+            </p>
+          </div>
+        ) : (
+          <div className="space-y-6">
+            {sortedDates.map((date) => (
+              <div key={date}>
+                <h3 className="text-sm font-semibold text-slate-900 mb-3 uppercase tracking-wide">
+                  {date}
+                </h3>
+                <div className="grid grid-cols-1 md:grid-cols-2 gap-3">
+                  {slotsByDate[date].map((slot) => (
+                    <SlotPickerTile
+                      key={slot.slot_instance_id}
+                      slot={slot}
+                      bookingId={bookingId}
+                      selected={selectedSlotId === slot.slot_instance_id}
+                      onSelect={setSelectedSlotId}
+                      onValidationResult={handleValidationResult}
+                    />
+                  ))}
+                </div>
+              </div>
+            ))}
+          </div>
+        )}
+
+        {/* Actions */}
+        <div className="mt-8 flex items-center justify-between pt-6 border-t border-slate-200">
+          <button
+            onClick={onCancel}
+            disabled={loading}
+            className="px-6 py-3 bg-slate-200 text-slate-700 font-semibold rounded-lg hover:bg-slate-300 transition-colors disabled:opacity-50"
+          >
+            Cancel
+          </button>
+
+          <button
+            onClick={handleConfirm}
+            disabled={!selectedSlotId || !isValid || loading}
+            className="px-6 py-3 bg-slate-900 text-white font-semibold rounded-lg hover:bg-slate-800 transition-colors disabled:opacity-50 disabled:cursor-not-allowed"
+          >
+            {loading ? (
+              <span className="flex items-center space-x-2">
+                <Loader2 className="w-4 h-4 animate-spin" />
+                <span>Moving...</span>
+              </span>
+            ) : (
+              'Confirm Move'
+            )}
+          </button>
+        </div>
+      </div>
+    </div>
+  );
+}

src/components/bookings/SlotPickerTile.tsx

@@ -0,0 +1,178 @@
+/**
+ * Slot Picker Tile Component
+ *
+ * Individual slot tile with dry_run validation feedback.
+ * Shows checkmark/error badges based on move validation.
+ */
+
+'use client';
+
+import { useState, useEffect } from 'react';
+import { Check, X, Loader2 } from 'lucide-react';
+import type { BookingSlot } from '@/src/types/bookings';
+import { validateMoveBooking } from '@/src/lib/api/bookings';
+import { getBookingErrorMessage } from '@/src/types/bookings';
+import CapacityDisplay from './CapacityDisplay';
+
+interface SlotPickerTileProps {
+  slot: Pick<
+    BookingSlot,
+    'slot_instance_id' | 'starts_at' | 'ends_at' | 'capacity' | 'booked_count' | 'capacity_remaining' | 'status'
+  > & {
+    court: {
+      court_id: number;
+      name: string;
+    };
+  };
+  bookingId: number;
+  selected: boolean;
+  onSelect: (slotInstanceId: number) => void;
+  onValidationResult?: (valid: boolean, reasons?: string[]) => void;
+}
+
+type ValidationState = 'idle' | 'validating' | 'valid' | 'invalid';
+
+export default function SlotPickerTile({
+  slot,
+  bookingId,
+  selected,
+  onSelect,
+  onValidationResult,
+}: SlotPickerTileProps) {
+  const [validationState, setValidationState] = useState<ValidationState>('idle');
+  const [validationReasons, setValidationReasons] = useState<string[]>([]);
+
+  // Run validation when tile is selected
+  useEffect(() => {
+    if (selected) {
+      runValidation();
+    } else {
+      // Reset validation when deselected
+      setValidationState('idle');
+      setValidationReasons([]);
+    }
+  }, [selected, slot.slot_instance_id]);
+
+  async function runValidation() {
+    setValidationState('validating');
+    setValidationReasons([]);
+
+    const result = await validateMoveBooking(bookingId, {
+      new_slot_instance_id: slot.slot_instance_id,
+    });
+
+    if (result.success) {
+      if (result.data.ok) {
+        setValidationState('valid');
+        setValidationReasons([]);
+        onValidationResult?.(true);
+      } else {
+        setValidationState('invalid');
+        setValidationReasons(result.data.reasons || []);
+        onValidationResult?.(false, result.data.reasons);
+      }
+    } else {
+      // Validation request failed - treat as invalid
+      setValidationState('invalid');
+      const errorMessage = getBookingErrorMessage(result.error);
+      setValidationReasons([errorMessage]);
+      onValidationResult?.(false, [errorMessage]);
+    }
+  }
+
+  function formatTime(isoString: string): string {
+    const date = new Date(isoString);
+    return date.toLocaleTimeString('en-US', {
+      hour: 'numeric',
+      minute: '2-digit',
+    });
+  }
+
+  function handleClick() {
+    onSelect(slot.slot_instance_id);
+  }
+
+  // Determine tile appearance based on validation state
+  const isDisabled = slot.status !== 'open' || slot.capacity_remaining === 0;
+  const borderColor = selected
+    ? validationState === 'valid'
+      ? 'border-green-500'
+      : validationState === 'invalid'
+      ? 'border-red-500'
+      : 'border-slate-900'
+    : 'border-slate-200';
+
+  const bgColor = selected
+    ? validationState === 'valid'
+      ? 'bg-green-50'
+      : validationState === 'invalid'
+      ? 'bg-red-50'
+      : 'bg-slate-50'
+    : 'bg-white';
+
+  return (
+    <button
+      onClick={handleClick}
+      disabled={isDisabled}
+      className={`w-full text-left border-2 rounded-lg p-4 transition-all ${borderColor} ${bgColor} ${
+        isDisabled
+          ? 'opacity-50 cursor-not-allowed'
+          : 'hover:border-slate-300 hover:shadow-sm cursor-pointer'
+      } ${selected ? 'shadow-md' : ''}`}
+    >
+      <div className="flex items-start justify-between mb-3">
+        <div className="flex-1">
+          <p className="text-sm font-semibold text-slate-900 mb-1">{slot.court.name}</p>
+          <p className="text-xs text-slate-600">
+            {formatTime(slot.starts_at)} - {formatTime(slot.ends_at)}
+          </p>
+        </div>
+
+        {/* Validation Badge */}
+        {selected && (
+          <div className="ml-3">
+            {validationState === 'validating' && (
+              <div className="flex items-center justify-center w-6 h-6 bg-slate-200 rounded-full">
+                <Loader2 className="w-4 h-4 text-slate-600 animate-spin" />
+              </div>
+            )}
+            {validationState === 'valid' && (
+              <div className="flex items-center justify-center w-6 h-6 bg-green-500 rounded-full">
+                <Check className="w-4 h-4 text-white" />
+              </div>
+            )}
+            {validationState === 'invalid' && (
+              <div className="flex items-center justify-center w-6 h-6 bg-red-500 rounded-full">
+                <X className="w-4 h-4 text-white" />
+              </div>
+            )}
+          </div>
+        )}
+      </div>
+
+      {/* Capacity */}
+      <CapacityDisplay slot={slot} variant="compact" />
+
+      {/* Validation Errors */}
+      {selected && validationState === 'invalid' && validationReasons.length > 0 && (
+        <div className="mt-3 pt-3 border-t border-red-200">
+          <ul className="space-y-1">
+            {validationReasons.map((reason, index) => (
+              <li key={index} className="text-xs text-red-700 flex items-start">
+                <span className="mr-1">•</span>
+                <span>{reason}</span>
+              </li>
+            ))}
+          </ul>
+        </div>
+      )}
+
+      {/* Success Message */}
+      {selected && validationState === 'valid' && (
+        <div className="mt-3 pt-3 border-t border-green-200">
+          <p className="text-xs text-green-700 font-medium">✓ Valid - ready to confirm</p>
+        </div>
+      )}
+    </button>
+  );
+}