feat: local sections in sub-events can use festival-level time slots

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

api/app/Http/Controllers/Api/V1/TimeSlotController.php

@@ -22,6 +22,22 @@ final class TimeSlotController extends Controller
 
         $timeSlots = $event->timeSlots()->orderBy('date')->orderBy('start_time')->get();
 
+        if ($event->isSubEvent() && request()->boolean('include_parent') && $event->parent_event_id) {
+            $parentTimeSlots = TimeSlot::where('event_id', $event->parent_event_id)
+                ->with('event')
+                ->orderBy('date')
+                ->orderBy('start_time')
+                ->get();
+
+            $timeSlots->load('event');
+            $timeSlots->each(fn (TimeSlot $ts) => $ts->setAttribute('source', 'sub_event'));
+            $parentTimeSlots->each(fn (TimeSlot $ts) => $ts->setAttribute('source', 'festival'));
+
+            $timeSlots = $timeSlots->merge($parentTimeSlots)
+                ->sortBy([['date', 'asc'], ['start_time', 'asc']])
+                ->values();
+        }
+
         return TimeSlotResource::collection($timeSlots);
     }