✨ Add leader-based permissions to Meetup event tests and editable scope

- 🔒 Ensure leader users are required for Meetup event tests to simulate accurate permissions.
- ➕ Add `editableBy` scope to `MeetupEvent` model for consistent editable event handling.
- 🛠️ Refactor `mine` API endpoint and MCP tool to leverage `editableBy` scope.
- 🧪 Update tests to verify leader-based accessibility for Meetup events.

app/Models/Meetup.php

@@ -292,7 +292,7 @@ class Meetup extends Model implements HasMedia
      */
     public function scopeLedBy(Builder $query, int $userId): void
     {
-        $query->whereHas('users', fn (Builder $user) => $user->whereKey($userId)->wherePivot('is_leader', true));
+        $query->whereHas('users', fn (Builder $user) => $user->whereKey($userId)->where('meetup_user.is_leader', true));
     }
 
     /**