✨ 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.

resources/views/livewire/meetups/landingpage.blade.php

@@ -23,7 +23,7 @@ class extends Component {
 
     public function deleteEvent(MeetupEvent $event): void
     {
-        if ($this->meetup->belongsToMe) {
+        if ($this->meetup->leadByMe) {
             $event->delete();
             $this->dispatch('event-deleted');
             Flux::modals()->close();
@@ -231,7 +231,7 @@ class extends Component {
         <div class="mt-16">
             <div class="flex flex-col sm:flex-row items-center sm:space-x-4 space-y-4 sm:space-y-0 mb-6">
                 <flux:heading size="xl">{{ __('Kommende Veranstaltungen') }}</flux:heading>
-                @if(auth()->user() && auth()->user()->meetups()->find($meetup->id)?->exists)
+                @if($meetup->leadByMe)
                     <flux:button :href="route_with_country('meetups.events.create', ['meetup' => $meetup])"
                                  variant="primary" icon="calendar">
                         {{ __('Neues Event erstellen') }}
@@ -281,7 +281,7 @@ class extends Component {
                             >
                                 {{ __('Öffnen/RSVP') }}
                             </flux:button>
-                            @if($meetup->belongsToMe)
+                            @if($meetup->leadByMe)
                                 <flux:button
                                     :href="route_with_country('meetups.events.edit', ['meetup' => $meetup, 'event' => $event])"
                                     size="xs"
@@ -332,7 +332,7 @@ class extends Component {
     @else
         <div class="mt-16">
             <div class="flex items-center space-x-4 mb-6">
-                @if(auth()->user() && auth()->user()->meetups()->find($meetup->id)?->exists)
+                @if($meetup->leadByMe)
                     <flux:button :href="route_with_country('meetups.events.create', ['meetup' => $meetup])"
                                  variant="primary" icon="calendar">
                         {{ __('Neues Event erstellen') }}