fix: rename preset to pattern_type in generate request (BREAKING CHANGE)

Backend API changed field name from "preset" to "pattern_type" in the
generate slot definitions endpoint (BUILD:347).

Changes:
- Updated GenerateSlotDefinitionsRequest interface: preset → pattern_type
- Updated GenerateSlotDefinitionsModal to send pattern_type in request body

This fixes compatibility with the updated backend API contract.

src/app/[locale]/admin/clubs/[club_id]/slot-definitions/GenerateSlotDefinitionsModal.tsx

@@ -113,7 +113,7 @@ export default function GenerateSlotDefinitionsModal({
     setError(null);
 
     const request: GenerateSlotDefinitionsRequest = {
-      preset,
+      pattern_type: preset,
       court_ids: selectedCourtIds,
       pattern_overrides: buildPatternOverrides(),
     };

src/types/slot-definitions.ts

@@ -147,7 +147,7 @@ export interface PatternOverrides {
  * Generate endpoint request
  */
 export interface GenerateSlotDefinitionsRequest {
-  preset: SlotDefinitionPreset;
+  pattern_type: SlotDefinitionPreset;
   court_ids: number[];
   pattern_overrides?: PatternOverrides;
   valid_from?: string; // YYYY-MM-DD