fix: add type safety to PlaybackPositionService and clarify watched state logic

- Move PlaybackPositionData interface to shared-interfaces lib
- Replace all `any` types with proper PlaybackPositionData typing
- Add comment clarifying position=duration semantics for watched episodes

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

libs/shared/interfaces/src/index.ts

@@ -10,6 +10,7 @@ export * from './lib/ipc-command.class';
 export * from './lib/ipc-commands';
 export * from './lib/language.enum';
 export * from './lib/parsed-playlist.interface';
+export * from './lib/playback-position.interface';
 export * from './lib/playlist-meta.type';
 export * from './lib/playlist.interface';
 export * from './lib/settings.interface';

libs/shared/interfaces/src/lib/playback-position.interface.ts

@@ -0,0 +1,14 @@
+/**
+ * Playback position data for resume functionality
+ */
+export interface PlaybackPositionData {
+    contentXtreamId: number;
+    contentType: 'vod' | 'episode';
+    seriesXtreamId?: number;
+    seasonNumber?: number;
+    episodeNumber?: number;
+    positionSeconds: number;
+    durationSeconds?: number;
+    playlistId?: string;
+    updatedAt?: string;
+}