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/TimeSlot.php

@@ -0,0 +1,57 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Builder;
+use Illuminate\Database\Eloquent\Concerns\HasUlids;
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Support\Carbon;
+
+final class TimeSlot extends Model
+{
+    use HasFactory;
+    use HasUlids;
+
+    protected $fillable = [
+        'event_id',
+        'name',
+        'person_type',
+        'date',
+        'start_time',
+        'end_time',
+        'duration_hours',
+    ];
+
+    protected function casts(): array
+    {
+        return [
+            'date' => 'date',
+            'person_type' => 'string',
+        ];
+    }
+
+    public function event(): BelongsTo
+    {
+        return $this->belongsTo(Event::class);
+    }
+
+    public function shifts(): HasMany
+    {
+        return $this->hasMany(Shift::class);
+    }
+
+    public function scopeForType(Builder $query, string $type): Builder
+    {
+        return $query->where('person_type', $type);
+    }
+
+    public function scopeForDate(Builder $query, Carbon $date): Builder
+    {
+        return $query->whereDate('date', $date);
+    }
+}