feat: schema v1.7 + sections/shifts frontend

- Universeel festival/event model (parent_event_id, event_type)
- event_person_activations pivot tabel
- Event model: parent/children relaties + helper scopes
- DevSeeder: festival structuur met sub-events
- Sections & Shifts frontend (twee-kolom layout)
- BACKLOG.md aangemaakt met 22 gedocumenteerde wensen

api/app/Models/Event.php

@@ -21,12 +21,19 @@ final class Event extends Model
 
     protected $fillable = [
         'organisation_id',
+        'parent_event_id',
         'name',
         'slug',
         'start_date',
         'end_date',
         'timezone',
         'status',
+        'event_type',
+        'event_type_label',
+        'sub_event_label',
+        'is_recurring',
+        'recurrence_rule',
+        'recurrence_exceptions',
     ];
 
     protected function casts(): array
@@ -34,6 +41,9 @@ final class Event extends Model
         return [
             'start_date' => 'date',
             'end_date' => 'date',
+            'is_recurring' => 'boolean',
+            'recurrence_exceptions' => 'array',
+            'event_type' => 'string',
         ];
     }
 
@@ -79,6 +89,68 @@ final class Event extends Model
         return $this->hasMany(CrowdList::class);
     }
 
+    public function parent(): BelongsTo
+    {
+        return $this->belongsTo(Event::class, 'parent_event_id');
+    }
+
+    public function children(): HasMany
+    {
+        return $this->hasMany(Event::class, 'parent_event_id')
+            ->orderBy('start_date')
+            ->orderBy('name');
+    }
+
+    // ----- Scopes -----
+
+    public function scopeTopLevel(Builder $query): Builder
+    {
+        return $query->whereNull('parent_event_id');
+    }
+
+    public function scopeChildren(Builder $query): Builder
+    {
+        return $query->whereNotNull('parent_event_id');
+    }
+
+    public function scopeFestivals(Builder $query): Builder
+    {
+        return $query->whereIn('event_type', ['festival', 'series']);
+    }
+
+    public function scopeWithChildren(Builder $query): Builder
+    {
+        return $query->where(function (Builder $q) {
+            $q->whereIn('id', function ($sub) {
+                $sub->select('id')->from('events')->whereNull('parent_event_id');
+            })->orWhereIn('parent_event_id', function ($sub) {
+                $sub->select('id')->from('events')->whereNull('parent_event_id');
+            });
+        });
+    }
+
+    // ----- Helpers -----
+
+    public function isFestival(): bool
+    {
+        return $this->event_type !== 'event' && $this->parent_event_id === null;
+    }
+
+    public function isSubEvent(): bool
+    {
+        return $this->parent_event_id !== null;
+    }
+
+    public function isFlatEvent(): bool
+    {
+        return $this->parent_event_id === null && $this->children()->count() === 0;
+    }
+
+    public function hasChildren(): bool
+    {
+        return $this->children()->exists();
+    }
+
     public function scopeDraft(Builder $query): Builder
     {
         return $query->where('status', 'draft');