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>

apps/web/src/app/xtream-tauri/data-sources/xtream-data-source.interface.ts

@@ -1,10 +1,14 @@
 import { InjectionToken } from '@angular/core';
 import {
+    PlaybackPositionData,
     XtreamCategory,
     XtreamLiveStream,
     XtreamSerieItem,
     XtreamVodStream,
 } from 'shared-interfaces';
+
+// Re-export for backward compatibility
+export { PlaybackPositionData };
 import { XtreamCredentials, CategoryType, StreamType } from '../services/xtream-api.service';
 
 /**
@@ -75,21 +79,6 @@ export interface RecentlyViewedItem extends XtreamContentItem {
     viewed_at: string;
 }
 
-/**
- * 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;
-}
-
 /**
  * Database category type mapping (differs from API type)
  */

apps/web/src/app/xtream-tauri/stores/features/with-playback-positions.feature.ts

@@ -318,6 +318,7 @@ export function withPlaybackPositions() {
 
                         if (duration === 0) duration = 1; // Fallback
 
+                        // Setting position = duration indicates episode is fully watched
                         const data: PlaybackPositionData = {
                             contentXtreamId: id,
                             contentType: 'episode',