Fix Jellyfin playlist track fetch truncating at default API limit

get_playlist_tracks() had no Limit or StartIndex params, so Jellyfin
defaulted to ~100 items per response. This caused the Server Playlists
comparison to show most tracks as missing even though they were present.

Now paginates in batches of 1000 until a partial batch signals the last page.

core/jellyfin_client.py

@@ -1472,23 +1472,34 @@ class JellyfinClient:
             return []
 
         try:
+            tracks = []
+            start_index = 0
+            limit = 1000
+
+            while True:
                 params = {
                     'ParentId': playlist_id,
                     'IncludeItemTypes': 'Audio',
                     'Recursive': True,
                     'Fields': 'AlbumId,ArtistItems,Path,MediaSources',
                     'SortBy': 'SortName',
-                'SortOrder': 'Ascending'
+                    'SortOrder': 'Ascending',
+                    'StartIndex': start_index,
+                    'Limit': limit,
                 }
 
                 response = self._make_request(f'/Users/{self.user_id}/Items', params)
                 if not response:
-                return []
+                    break
 
-            tracks = []
+                batch = response.get('Items', [])
-            for item in response.get('Items', []):
+                for item in batch:
                     tracks.append(JellyfinTrack(item, self))
 
+                if len(batch) < limit:
+                    break  # Last page
+                start_index += limit
+
             logger.debug(f"Retrieved {len(tracks)} tracks from playlist {playlist_id}")
             return tracks