✨ **Add authenticated API endpoints for managing Meetups, Cities, Venues, and Lecturers**

- ➕ Introduced `store`, `update`, `mine`, and `mineShow` endpoints for `Meetups`, `Cities`, `Venues`, and `Lecturers` with validation and authorization.
- 🔒 Added `Policies` for `Meetups`, `Cities`, `Venues`, and `Lecturers` leveraging `ChecksCreatorOwnership` for ownership checks.
- 🌐 Created `Resources` for structured API responses: `MeetupResource`, `CityResource`, `VenueResource`, and `LecturerResource`.
- ✅ Added dedicated `Request` classes for input validation: `Store` and `Update` variants for all models.
- 🛠️ Updated controllers to support new functionalities with localized error messages and proper HTTP responses.

app/Policies/Concerns/ChecksCreatorOwnership.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace App\Policies\Concerns;
+
+use App\Models\User;
+use Illuminate\Database\Eloquent\Model;
+
+trait ChecksCreatorOwnership
+{
+    /**
+     * Nur der urspruengliche Ersteller (created_by) oder ein Super-Admin darf das Model veraendern.
+     */
+    protected function owns(User $user, Model $model): bool
+    {
+        return (int) $model->created_by === $user->id || $user->hasRole('super-admin');
+    }
+}