feat(settings): enable desktop remote control and change port

Update default remote control port from 3000 to 8765 in settings
store and component initialization to avoid conflicts with common
development ports and align with the desktop/tauri environment.

Unhide and scope the remote control UI to desktop builds only:
- Restore the remote control block in settings template and guard it
  with @if (isDesktop) so the checkbox and description render for
  desktop users (previously commented out as not ported).
- Keep the remote control settings section conditionally visible
  when the remoteControl form value is true.

These changes ensure desktop users can configure and enable the
remote control feature with a non-conflicting default port.

apps/web/src/app/settings/settings.component.ts

@@ -144,7 +144,15 @@ export class SettingsComponent implements OnInit {
         mpvReuseInstance: false,
         vlcPlayerPath: '',
         remoteControl: false,
-        remoteControlPort: 3000,
+        remoteControlPort: [
+            8765,
+            [
+                Validators.required,
+                Validators.min(1),
+                Validators.max(65535),
+                Validators.pattern(/^\d+$/),
+            ],
+        ],
     });
 
     /** Form array with epg sources */