feat: fix time slot hierarchy — seeder, API include_children, frontend dropdown, navigation

Restructure the festival hierarchy end-to-end:

Seeder: Remove duplicate festival-level VOLUNTEER time slots, keep only CREW
operational slots. Rename sub-events to "Dag 1/2/3 — ..." pattern. Change
Nachtsecurity to Security (cross_event). EHBO/Security shifts now use sub-event
time slots via cross_event exception. Add flat event "Braderie Dorpstown 2026".

API: Add ?include_children=true to TimeSlotController for festivals, returning
all sub-event time slots with source and event_name fields. Update
StoreShiftRequest and UpdateShiftRequest to accept child time slots for
cross_event sections.

Frontend: Create useTimeSlotDropdown composable with 4-scenario dropdown logic.
Replace AppSelect with VAutocomplete in CreateShiftDialog with grouped items,
dimmed festival slots, and info tooltips. Add InfoTooltip reusable component.
Show festival context labels on cross_event sections in sub-event section lists.
Add read-only festival time slots on sub-event time-slots page. Add cross_event
context banner with "Bekijk alle diensten" link.

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

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

@@ -34,6 +34,7 @@ final class TimeSlotController extends Controller
             ->orderBy('start_time')
             ->get();
 
+        // For sub-events: include parent festival time slots
         if ($event->isSubEvent() && request()->boolean('include_parent') && $event->parent_event_id) {
             $parentTimeSlots = TimeSlot::where('event_id', $event->parent_event_id)
                 ->withCount('shifts')
@@ -56,6 +57,35 @@ final class TimeSlotController extends Controller
                 ->values();
         }
 
+        // For festivals: include all sub-event time slots (for cross_event section shift dialogs)
+        if (!$event->isSubEvent() && request()->boolean('include_children')) {
+            $childEventIds = Event::where('parent_event_id', $event->id)->pluck('id');
+
+            if ($childEventIds->isNotEmpty()) {
+                $childTimeSlots = TimeSlot::whereIn('event_id', $childEventIds)
+                    ->withCount('shifts')
+                    ->with([
+                        'event',
+                        'shifts' => fn ($q) => $q->withCount([
+                            'shiftAssignments as assignments_count' => fn ($q) => $q->where('status', 'approved'),
+                        ]),
+                    ])
+                    ->orderBy('date')
+                    ->orderBy('start_time')
+                    ->get();
+
+                $timeSlots->load('event');
+                $timeSlots->each(fn (TimeSlot $ts) => $ts->setAttribute('source', 'own'));
+                $childTimeSlots->each(function (TimeSlot $ts) use ($event) {
+                    $ts->setAttribute('source', $ts->event_id);
+                });
+
+                $timeSlots = $timeSlots->merge($childTimeSlots)
+                    ->sortBy([['date', 'asc'], ['start_time', 'asc']])
+                    ->values();
+            }
+        }
+
         return TimeSlotResource::collection($timeSlots);
     }