feat: Phase 2 - Laravel Reverb + real-time notifications

- Install laravel/reverb + laravel-echo + pusher-js
- Configure broadcasting to reverb in .env.example + .env
- Add Echo + Pusher client in resources/js/app.js
- Update all 14 notifications to implement ShouldBroadcast + broadcastOn()
- Update NotificationBell component to listen for real-time events
- Add Livewire.emit in notification-bell blade for JS-to-Livewire bridge

Tests: 101 passing (319 assertions)

resources/views/livewire/common/notification-bell.blade.php

@@ -84,4 +84,18 @@
             @endif
         </div>
     </div>
+
+    @push('scripts')
+    <script>
+        document.addEventListener('livewire:load', () => {
+            const userId = {{ auth()->id() ?? 'null' }};
+            if (userId && window.Echo) {
+                window.Echo.private(`user.${userId}`)
+                    .notification((notification) => {
+                        Livewire.emit('notification-received', notification.data.message ?? 'Nueva notificación');
+                    });
+            }
+        });
+    </script>
+    @endpush
 </div>