fix: pass audio/video URL params to EC for correct initial device state

- Camera no longer starts enabled when user disables it in prescreen
- When PTT mode is enabled, call starts muted so PTT works immediately
  without requiring a manual mute first
- CallControlState also updated to match the forced-off audio for PTT

EC 0.16.x ignores io.element.device_mute for initial state at startup,
so audio= and video= URL params are the only reliable way to set the
initial device state before the call begins.

src/app/plugins/call/CallEmbed.ts

@@ -60,7 +60,9 @@ export class CallEmbed {
     room: Room,
     intent: ElementCallIntent,
     themeKind: ElementCallThemeKind,
-    noiseSuppression = true
+    noiseSuppression = true,
+    initialAudio = true,
+    initialVideo = false
   ): Widget {
     const userId = mx.getSafeUserId();
     const deviceId = mx.getDeviceId() ?? '';
@@ -83,6 +85,8 @@ export class CallEmbed {
       lang: 'en-EN',
       theme: themeKind,
       noiseSuppression: noiseSuppression.toString(),
+      audio: initialAudio.toString(),
+      video: initialVideo.toString(),
     });
 
     const widgetUrl = new URL(