feat(call): PTT, deafen label, camera default off, screenshare confirm, noise suppression setting

- Push to Talk: keydown/keyup binds mic to configurable key (default Space)
  with visual PTT indicator and key-binding UI in Settings > General > Calls
- Camera always defaults OFF on join; cameraOnJoin setting for explicit opt-in
- Deafen button tooltip corrected to Deafen/Undeafen instead of Turn Off/On Sound
- Screenshare confirmation dialog before broadcasting to call participants
- Noise suppression toggle wired from settings through CallEmbed URL params
- CallControl.setMicrophone() public method for programmatic mic control
- Calls settings section added to General settings page

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/plugins/call/CallControl.ts

@@ -173,6 +173,14 @@ export class CallControl extends EventEmitter implements CallControlState {
     this.emitStateUpdate();
   }
 
+  public setMicrophone(enabled: boolean) {
+    const payload: ElementMediaStatePayload = {
+      audio_enabled: enabled,
+      video_enabled: this.video,
+    };
+    return this.setMediaState(payload);
+  }
+
   public toggleMicrophone() {
     const payload: ElementMediaStatePayload = {
       audio_enabled: !this.microphone,