feat: add slug field to events and implement tests for slug uniqueness per tenant

database/migrations/2026_09_22_010000_add_slugs_to_events.php

@@ -11,14 +11,14 @@ return new class extends Migration
     public function up(): void
     {
         Schema::table('events', function (Blueprint $table): void {
-            $table->string('slug')->nullable()->after('tenant_code');
+            $table->string('slug')->nullable();
         });
 
         $usedSlugsByTenant = [];
 
         foreach (DB::table('events')->orderBy('tenant_code')->orderBy('id')->get() as $event) {
             $baseSlug = Str::slug((string) $event->title);
-            $baseSlug = $baseSlug !== '' ? mb_substr($baseSlug, 0, 240) : 'evento-'.$event->id;
+            $baseSlug = $baseSlug !== '' ? substr($baseSlug, 0, 240) : 'evento-'.$event->id;
             $slug = $baseSlug;
             $suffix = 2;