fix(playback): keep the display awake while built-in players play video

Closes #1095. The renderer tracks every playing <video> through
document-level capture listeners (element-level release listeners catch
the detached-element pause on component teardown) and, while any video
is playing and the document is visible, holds a display-sleep lock:
a main-process powerSaveBlocker over IPC in Electron — reliable on
Linux where Chromium's own video wake lock depends on DE D-Bus
inhibitors — and the Screen Wake Lock API in the PWA. The vote is
auto-cleared when the renderer reloads or dies. Radio's <audio>
deliberately never blocks display sleep; embedded MPV and external
MPV/VLC already manage their own inhibition.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

libs/shared/interfaces/src/lib/electron-api.interface.ts

@@ -639,6 +639,14 @@ export interface ElectronBridgeApi {
     onWindowCloseRequested: (
         callback: (requestId: number) => void
     ) => () => void;
+    /**
+     * While active, the main process holds a
+     * `powerSaveBlocker('prevent-display-sleep')` so the screen stays awake
+     * during built-in video playback. The flag is cleared automatically when
+     * the renderer navigates, reloads, or dies, so a crashed page can never
+     * leave the display pinned awake.
+     */
+    setPlaybackKeepAwake: (active: boolean) => Promise<void>;
     fetchPlaylistByUrl: (
         url: string,
         title?: string,

libs/shared/interfaces/src/lib/ipc-commands.ts

@@ -107,6 +107,10 @@ export const DELETE_ALL_PLAYLISTS = 'DELETE_ALL_PLAYLISTS';
 // Remote Control
 export const REMOTE_CONTROL_CHANGE_CHANNEL = 'REMOTE_CONTROL_CHANGE_CHANNEL';
 
+// Display sleep: while a built-in video player is playing, the renderer asks
+// the main process to hold a powerSaveBlocker so the screen stays awake
+export const PLAYBACK_SET_KEEP_AWAKE = 'PLAYBACK:SET_KEEP_AWAKE';
+
 // Window controls (custom title bar on Windows/Linux)
 export const WINDOW_MINIMIZE = 'WINDOW:MINIMIZE';
 export const WINDOW_TOGGLE_MAXIMIZE = 'WINDOW:TOGGLE_MAXIMIZE';