feat(core,web): player queue, play events and web player controller (M3, wip)

- core: PlayQueue with shuffle and repeat, PlayAttempt counting only
  time actually played, EventBuffer with batching and backoff, uuidv7
- web: Player over HTMLAudioElement with Media Session, preload of the
  next track, expired-link refresh, local and server playback state,
  hotkeys; PlayerProvider is not wired into the shell yet
- ru/en strings and icons for the player and Collection

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/core/src/index.ts

@@ -10,4 +10,15 @@ export {
   type ClientType,
   type RefreshStore,
 } from './auth';
+export {
+  EventBuffer,
+  PlayAttempt,
+  PlayQueue,
+  uuidv7,
+  type EventSink,
+  type PlayContext,
+  type PlayEvent,
+  type RepeatMode,
+  type Track,
+} from './player';
 export { checkServer, normalizeServerUrl, SERVER_CHECK_TIMEOUT_MS, type ServerCheck } from './server';