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)

bootstrap/app.php

@@ -17,6 +17,7 @@ return Application::configure(basePath: dirname(__DIR__))
         web: __DIR__.'/../routes/web.php',
         api: __DIR__.'/../routes/api.php',
         commands: __DIR__.'/../routes/console.php',
+        channels: __DIR__.'/../routes/channels.php',
         health: '/up',
     )
     ->withMiddleware(function (Middleware $middleware): void {