feat(player): guard against audio playback on secondary device

frontend/angular/src/app/features/player/player-shell.component.ts

@@ -113,6 +113,7 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
   private reconnectTimer: ReturnType<typeof setTimeout> | null = null;
   private stateSyncTimer: ReturnType<typeof setTimeout> | null = null;
   private unsubscribeLocale: (() => void) | null = null;
+  private restoreAudioGuard: (() => void) | null = null;
 
   constructor() {
     if (typeof navigator !== 'undefined' && !navigator.onLine) {
@@ -129,6 +130,7 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
     this.unsubscribeLocale = subscribeToLocaleChanges((locale) => {
       this.locale = locale;
     });
+    this.installSecondaryDeviceAudioGuard();
 
     const hashRoute = window.location.hash.replace(/^#\/?/, '');
     const match = hashRoute.match(/^player(?:\/[^/]+)?(?:\/([^/?#]+))?/i);
@@ -158,6 +160,8 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
     this.clearStateSyncTimer();
     this.unsubscribeLocale?.();
     this.unsubscribeLocale = null;
+    this.restoreAudioGuard?.();
+    this.restoreAudioGuard = null;
   }
 
   private readonly handleOnline = (): void => {
@@ -185,6 +189,25 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
     }
   }
 
+  private installSecondaryDeviceAudioGuard(): void {
+    if (!this.clientHasNoAudioOutput || typeof window === 'undefined') {
+      return;
+    }
+
+    const mediaPrototype = (window as Window & { HTMLMediaElement?: { prototype?: { play?: () => Promise<void> } } }).HTMLMediaElement
+      ?.prototype;
+
+    if (!mediaPrototype || typeof mediaPrototype.play !== 'function') {
+      return;
+    }
+
+    const originalPlay = mediaPrototype.play;
+    mediaPrototype.play = () => Promise.resolve();
+    this.restoreAudioGuard = () => {
+      mediaPrototype.play = originalPlay;
+    };
+  }
+
   private scheduleStateSync(): void {
     this.clearStateSyncTimer();