feat(api): Implement API Resource Standard compliance

- Create BaseResource with formatDate() and formatDecimal() utilities
- Create 11 API Resource classes for all models
- Update all 6 controllers to return wrapped responses via wrapResource()
- Update frontend API client with unwrapResponse() helper
- Update all 63+ backend tests to expect 'data' wrapper
- Regenerate Scribe API documentation

BREAKING CHANGE: All API responses now wrap data in 'data' key per architecture spec.

Backend Tests: 70 passed, 5 failed (unrelated to data wrapper)
Frontend Unit: 10 passed
E2E Tests: 102 passed, 20 skipped
API Docs: Generated successfully

Refs: openspec/changes/api-resource-standard

backend/app/Http/Controllers/Api/HolidayController.php

@@ -3,6 +3,7 @@
 namespace App\Http\Controllers\Api;
 
 use App\Http\Controllers\Controller;
+use App\Http\Resources\HolidayResource;
 use App\Models\Holiday;
 use App\Services\CapacityService;
 use Illuminate\Http\JsonResponse;
@@ -18,15 +19,19 @@ class HolidayController extends Controller
      * Retrieve holidays for a specific month or all holidays when no month is provided.
      *
      * @group Capacity Planning
+     *
      * @urlParam month string nullable The month in YYYY-MM format. Example: 2026-02
-     * @response [
-     *   {
-     *     "id": "550e8400-e29b-41d4-a716-446655440000",
-     *     "date": "2026-02-14",
-     *     "name": "Company Holiday",
-     *     "description": "Office closed"
-     *   }
-     * ]
+     *
+     * @response {
+     *   "data": [
+     *     {
+     *       "id": "550e8400-e29b-41d4-a716-446655440000",
+     *       "date": "2026-02-14",
+     *       "name": "Company Holiday",
+     *       "description": "Office closed"
+     *     }
+     *   ]
+     * }
      */
     public function index(Request $request): JsonResponse
     {
@@ -38,7 +43,7 @@ class HolidayController extends Controller
             ? $this->capacityService->getHolidaysForMonth($data['month'])
             : Holiday::orderBy('date')->get();
 
-        return response()->json($holidays);
+        return $this->wrapResource(HolidayResource::collection($holidays));
     }
 
     /**
@@ -47,14 +52,18 @@ class HolidayController extends Controller
      * Add a holiday and clear cached capacity data for the related month.
      *
      * @group Capacity Planning
+     *
      * @bodyParam date string required Date of the holiday. Example: 2026-02-14
      * @bodyParam name string required Name of the holiday. Example: Presidents' Day
      * @bodyParam description string nullable Optional description of the holiday.
+     *
      * @response 201 {
-     *   "id": "550e8400-e29b-41d4-a716-446655440000",
-     *   "date": "2026-02-14",
-     *   "name": "Presidents' Day",
-     *   "description": "Office closed"
+     *   "data": {
+     *     "id": "550e8400-e29b-41d4-a716-446655440000",
+     *     "date": "2026-02-14",
+     *     "name": "Presidents' Day",
+     *     "description": "Office closed"
+     *   }
      * }
      */
     public function store(Request $request): JsonResponse
@@ -68,7 +77,7 @@ class HolidayController extends Controller
         $holiday = Holiday::create($data);
         $this->capacityService->forgetCapacityCacheForMonth($holiday->date->format('Y-m'));
 
-        return response()->json($holiday, 201);
+        return $this->wrapResource(new HolidayResource($holiday), 201);
     }
 
     /**
@@ -77,7 +86,9 @@ class HolidayController extends Controller
      * Remove a holiday and clear affected capacity caches.
      *
      * @group Capacity Planning
+     *
      * @urlParam id string required The holiday UUID. Example: 550e8400-e29b-41d4-a716-446655440000
+     *
      * @response {
      *   "message": "Holiday deleted"
      * }