feat: fase 2 backend — crowd types, persons, sections, shifts, invite flow

- Crowd Types + Persons CRUD (73 tests)
- Festival Sections + Time Slots + Shifts CRUD met assign/claim flow (84 tests)
- Invite Flow + Member Management met InvitationService (109 tests)
- Schema v1.6 migraties volledig uitgevoerd
- DevSeeder bijgewerkt met crowd types voor testorganisatie

api/app/Models/Event.php

@@ -54,6 +54,31 @@ final class Event extends Model
         return $this->hasMany(UserInvitation::class);
     }
 
+    public function locations(): HasMany
+    {
+        return $this->hasMany(Location::class);
+    }
+
+    public function festivalSections(): HasMany
+    {
+        return $this->hasMany(FestivalSection::class);
+    }
+
+    public function timeSlots(): HasMany
+    {
+        return $this->hasMany(TimeSlot::class);
+    }
+
+    public function persons(): HasMany
+    {
+        return $this->hasMany(Person::class);
+    }
+
+    public function crowdLists(): HasMany
+    {
+        return $this->hasMany(CrowdList::class);
+    }
+
     public function scopeDraft(Builder $query): Builder
     {
         return $query->where('status', 'draft');