feat: add custom webhook notification support

Add basic infrastructure for custom webhook notifications:
- Create webhook_notification_settings table with event toggles
- Add WebhookNotificationSettings model with encrypted URL
- Integrate webhook settings into Team model and HasNotificationSettings trait
- Create Livewire component and Blade view for webhook configuration
- Add webhook navigation route and UI

This provides the foundation for sending webhook notifications to custom HTTP/HTTPS endpoints when events occur in Coolify.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

resources/views/components/notification/navbar.blade.php

@@ -23,6 +23,10 @@
                 href="{{ route('notifications.pushover') }}">
                 <button>Pushover</button>
             </a>
+            <a class="{{ request()->routeIs('notifications.webhook') ? 'dark:text-white' : '' }}"
+                href="{{ route('notifications.webhook') }}">
+                <button>Webhook</button>
+            </a>
         </nav>
     </div>
 </div>