✨ Implement leadership-based permissions for Meetup management

- 🔒 Restrict event creation, editing, and deletion to Meetup leaders (`is_leader`) and creators for consistency across APIs, frontend, and MCP.
- ➕ Add new APIs for leader delegation: assign/remove Meetup leaders via `meetup_user.is_leader`.
- 🛠️ Replace loose member checks with specific leadership checks in policies, controllers, and views.
- 🧪 Add exhaustive tests to ensure only eligible leaders execute critical actions (e.g., event creation/edit, Meetup updates).
- 🔄 Refactor pivot relationships and models (`leadByMe`, `isLeader`) for explicit leadership handling.
- ✨ Introduce artisan command `meetups:promote-existing-leaders` to transition legacy data.

app/Http/Requests/Api/StoreMeetupEventRequest.php

@@ -3,15 +3,23 @@
 namespace App\Http\Requests\Api;
 
 use App\Enums\RecurrenceType;
-use App\Models\MeetupEvent;
+use App\Models\Meetup;
 use Illuminate\Foundation\Http\FormRequest;
 use Illuminate\Validation\Rule;
 
 class StoreMeetupEventRequest extends FormRequest
 {
+    /**
+     * Termine darf nur anlegen, wer das zugehörige Meetup bearbeiten darf
+     * (Ersteller/Leader/Super-Admin) — dieselbe Berechtigung wie die
+     * Stammdaten. Existenz/Pflicht von meetup_id prüft rules() (422); ist ein
+     * gültiges Meetup angegeben, muss der Nutzer dafür berechtigt sein.
+     */
     public function authorize(): bool
     {
-        return $this->user()->can('create', MeetupEvent::class);
+        $meetup = Meetup::find($this->input('meetup_id'));
+
+        return $meetup === null || $this->user()->can('update', $meetup);
     }
 
     /**

app/Http/Requests/Api/StoreMeetupLeaderRequest.php

@@ -0,0 +1,41 @@
+<?php
+
+namespace App\Http\Requests\Api;
+
+use Closure;
+use Illuminate\Foundation\Http\FormRequest;
+use swentel\nostr\Key\Key as NostrKey;
+
+/**
+ * Setzt einen weiteren Leader für ein Meetup per Nostr-npub ein. Nur ein
+ * bestehender Leader (bzw. Ersteller/Super-Admin) darf das (manageLeaders).
+ * Der npub muss ein gültiger bech32-kodierter öffentlicher Schlüssel sein.
+ */
+class StoreMeetupLeaderRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return $this->user()->can('manageLeaders', $this->route('meetup'));
+    }
+
+    /**
+     * @return array<string, array<int, mixed>>
+     */
+    public function rules(): array
+    {
+        return [
+            'npub' => [
+                'required',
+                'string',
+                'starts_with:npub1',
+                function (string $attribute, mixed $value, Closure $fail): void {
+                    try {
+                        (new NostrKey)->convertToHex((string) $value);
+                    } catch (\Throwable) {
+                        $fail(__('Das ist kein gültiger npub.'));
+                    }
+                },
+            ],
+        ];
+    }
+}

app/Http/Requests/Api/UpdateMeetupEventRequest.php

@@ -3,14 +3,27 @@
 namespace App\Http\Requests\Api;
 
 use App\Enums\RecurrenceType;
+use App\Models\Meetup;
 use Illuminate\Foundation\Http\FormRequest;
 use Illuminate\Validation\Rule;
 
 class UpdateMeetupEventRequest extends FormRequest
 {
+    /**
+     * Bearbeiten darf der Ersteller des Termins oder ein Leader des Meetups
+     * (siehe MeetupEventPolicy::update). Ein Verschieben in ein anderes Meetup
+     * (geändertes meetup_id) ist nur erlaubt, wenn der Nutzer auch dieses
+     * Ziel-Meetup führt.
+     */
     public function authorize(): bool
     {
-        return $this->user()->can('update', $this->route('meetupEvent'));
+        if (! $this->user()->can('update', $this->route('meetupEvent'))) {
+            return false;
+        }
+
+        $target = $this->filled('meetup_id') ? Meetup::find($this->input('meetup_id')) : null;
+
+        return $target === null || $this->user()->can('update', $target);
     }
 
     /**