feat: audio devices + fullscreen + banner cleanup (v0.7.0)

Audio device selection:
- audioSettings: persisted inputDeviceId + outputDeviceId
- CallContext: uses stored input deviceId on mic enable, new
  setAudioInputDevice / setAudioOutputDevice actions that hot-swap
  without reconnect. Output swap applies HTMLMediaElement.setSinkId
  to every attached remote-audio element (LiveKit's switchActiveDevice
  only tracks elements it attached itself)
- SettingsPage: new "Mikrofon" + "Ausgabegerät" selects with
  enumerateDevices, devicechange listener, permission-probe button.
  setSinkId-unsupported fallback is messaged but non-blocking

Fullscreen:
- FullscreenCall was absolute inset-0 z-40 which trapped it inside the
  <main> pane — sidebar + chat-list stayed visible. Switched to
  fixed inset-0 z-[60] so the call overlays the whole window
  Discord-style
- ScreenShareViewer fullscreen: CSS-only toggle (native Fullscreen API
  unreliable under Tauri WKWebView), portalled to document.body when
  active so no ancestor stacking context can clip it. Esc exits

ActiveCallBanner:
- cleanup effect returned early when presence was entirely empty,
  leaving the "1 im Raum" fallback stuck after both peers left. Now
  schedules dismissLastCall as soon as othersIn.length === 0, with a
  3s grace window to absorb presence re-sync flicker

Bump tauri version 0.6.0 -> 0.7.0

apps/desktop/src/context/CallContext.tsx

@@ -40,6 +40,7 @@ import { getPttSettings, subscribePttSettings } from '../lib/pttSettings';
 import {
   getAudioQualityParams,
   getAudioSettings,
+  updateAudioSettings,
 } from '../lib/audioSettings';
 import {
   createCallE2EE,
@@ -120,6 +121,12 @@ interface CallContextValue {
   dismissLastCall: () => void;
   setCallMode: (mode: CallMode) => void;
   setFocusedId: (id: string | null) => void;
+  // Runtime mic switch. Persists choice so subsequent calls reuse it, and
+  // hot-swaps the input on an active call without a reconnect.
+  setAudioInputDevice: (deviceId: string | null) => Promise<void>;
+  // Runtime speaker/headphone switch. Persists + applies setSinkId to all
+  // currently-attached remote-audio elements.
+  setAudioOutputDevice: (deviceId: string | null) => Promise<void>;
 }
 
 const CallContext = createContext<CallContextValue | null>(null);
@@ -482,12 +489,16 @@ export function CallProvider({ children }: { children: ReactNode }) {
         setIsE2EEActive(false);
       }
       try {
+        const inputId = getAudioSettings().inputDeviceId;
         await r.localParticipant.setMicrophoneEnabled(true, {
           echoCancellation: aParams.echoCancellation,
           noiseSuppression: aParams.noiseSuppression,
           autoGainControl: aParams.autoGainControl,
           channelCount: aParams.stereo ? 2 : 1,
           sampleRate: aParams.sampleRateHz,
+          // Plain string maps to `ideal` — if the device is gone we fall back
+          // to OS default instead of throwing NotFoundError.
+          ...(inputId ? { deviceId: inputId } : {}),
         });
       } catch (micErr: unknown) {
         console.error('setMicrophoneEnabled failed', micErr);
@@ -973,6 +984,46 @@ export function CallProvider({ children }: { children: ReactNode }) {
     setFocusedIdState(id);
   }, []);
 
+  const setAudioInputDevice = useCallback(async (deviceId: string | null) => {
+    updateAudioSettings({ inputDeviceId: deviceId });
+    const r = roomRef.current;
+    if (!r) return;
+    try {
+      // LiveKit API: `switchActiveDevice(kind, deviceId)` hot-swaps without a
+      // reconnect. Pass empty string or `default` to revert to OS default.
+      await r.switchActiveDevice('audioinput', deviceId ?? 'default');
+    } catch (err: unknown) {
+      console.error('switchActiveDevice(audioinput) failed', err);
+    }
+  }, []);
+
+  const setAudioOutputDevice = useCallback(async (deviceId: string | null) => {
+    updateAudioSettings({ outputDeviceId: deviceId });
+    const sinkId = deviceId ?? '';
+    // Apply to every <audio> element we've attached to the body. LiveKit's
+    // switchActiveDevice only tracks elements it attached itself; our custom
+    // appendChild path bypasses that, so we iterate and setSinkId manually.
+    const els = document.querySelectorAll<HTMLAudioElement>(
+      'audio[data-livekit-track]',
+    );
+    for (const el of Array.from(els)) {
+      if (typeof el.setSinkId !== 'function') continue;
+      try {
+        await el.setSinkId(sinkId);
+      } catch (err: unknown) {
+        console.warn('setSinkId on audio element failed', err);
+      }
+    }
+    const r = roomRef.current;
+    if (r) {
+      try {
+        await r.switchActiveDevice('audiooutput', sinkId || 'default');
+      } catch (err: unknown) {
+        console.warn('switchActiveDevice(audiooutput) failed', err);
+      }
+    }
+  }, []);
+
   // Reset UI call-mode state when the call leaves any active phase so the next
   // call starts fresh at grid/unfocused.
   useEffect(() => {
@@ -1017,6 +1068,8 @@ export function CallProvider({ children }: { children: ReactNode }) {
       dismissLastCall,
       setCallMode,
       setFocusedId,
+      setAudioInputDevice,
+      setAudioOutputDevice,
     }),
     [
       state,
@@ -1039,6 +1092,8 @@ export function CallProvider({ children }: { children: ReactNode }) {
       dismissLastCall,
       setCallMode,
       setFocusedId,
+      setAudioInputDevice,
+      setAudioOutputDevice,
     ],
   );
 
@@ -1063,6 +1118,15 @@ function attachTrack(
       audio.setAttribute('playsinline', 'true');
       audio.setAttribute('data-livekit-track', track.sid ?? '');
       document.body.appendChild(audio);
+      // Apply persisted sinkId so the element routes to the user's chosen
+      // speaker/headphone from the start (LiveKit's own `switchActiveDevice`
+      // doesn't track custom-appended elements).
+      const sinkId = getAudioSettings().outputDeviceId;
+      if (sinkId && typeof audio.setSinkId === 'function') {
+        void audio.setSinkId(sinkId).catch((err: unknown) => {
+          console.warn('setSinkId on attach failed', err);
+        });
+      }
     }
   }
   // Video is handled later in M2.6/M3 by a dedicated <video> element.