Fix Navidrome full refresh importing albums from unselected music folders

The Subsonic getArtist endpoint doesn't support musicFolderId filtering,
so when an artist exists in multiple libraries, all their albums were
imported regardless of which music folder was selected in settings.

Now passes musicFolderId to getArtist (in case Navidrome supports it),
and as a fallback filters albums against a cached set of album IDs
built from getAlbumList2 (which reliably supports musicFolderId).
The set is built once per session and invalidated on folder change.

core/navidrome_client.py

@@ -155,6 +155,7 @@ class NavidromeClient:
         self._artist_cache = {}
         self._album_cache = {}
         self._track_cache = {}
+        self._folder_album_ids: Optional[set] = None  # Album IDs in selected music folder
 
         # Progress callback for UI updates
         self._progress_callback = None
@@ -173,6 +174,7 @@ class NavidromeClient:
         self._artist_cache.clear()
         self._album_cache.clear()
         self._track_cache.clear()
+        self._folder_album_ids = None
         logger.info("Navidrome client config reset — will reconnect with new settings")
 
     def get_music_folders(self) -> list:
@@ -199,6 +201,7 @@ class NavidromeClient:
             for folder in folders:
                 if folder['title'] == folder_name:
                     self.music_folder_id = folder['key']
+                    self._folder_album_ids = None  # Invalidate album filter cache
                     logger.info(f"Set music folder to: {folder_name} (ID: {self.music_folder_id})")
                     from database.music_database import MusicDatabase
                     db = MusicDatabase()
@@ -207,6 +210,7 @@ class NavidromeClient:
             # If folder_name is empty, clear the selection
             if not folder_name:
                 self.music_folder_id = None
+                self._folder_album_ids = None  # Invalidate album filter cache
                 from database.music_database import MusicDatabase
                 db = MusicDatabase()
                 db.set_preference('navidrome_music_folder', '')
@@ -486,7 +490,10 @@ class NavidromeClient:
             if self._progress_callback:
                 self._progress_callback(f"Fetching albums for artist {artist_name}...")
 
-            response = self._make_request('getArtist', {'id': artist_id})
+            params = {'id': artist_id}
+            if self.music_folder_id:
+                params['musicFolderId'] = self.music_folder_id
+            response = self._make_request('getArtist', params)
             if not response:
                 return []
 
@@ -500,6 +507,16 @@ class NavidromeClient:
             for album_data in album_list:
                 albums.append(NavidromeAlbum(album_data, self))
 
+            # Filter to selected music folder if Navidrome didn't handle musicFolderId
+            # on getArtist (not all Subsonic implementations support it on this endpoint)
+            if self.music_folder_id and albums:
+                folder_ids = self._get_folder_album_ids()
+                if folder_ids is not None:
+                    before = len(albums)
+                    albums = [a for a in albums if a.ratingKey in folder_ids]
+                    if len(albums) < before:
+                        logger.debug(f"Filtered {before - len(albums)} albums outside selected music folder for artist {artist_id}")
+
             # Cache the result
             self._album_cache[artist_id] = albums
 
@@ -509,6 +526,44 @@ class NavidromeClient:
             logger.error(f"Error getting albums for artist {artist_id}: {e}")
             return []
 
+    def _get_folder_album_ids(self) -> Optional[set]:
+        """Get set of album IDs belonging to the selected music folder.
+        Uses getAlbumList2 with musicFolderId to build the set, cached for reuse."""
+        if self._folder_album_ids is not None:
+            return self._folder_album_ids
+        if not self.music_folder_id:
+            return None
+        try:
+            album_ids = set()
+            offset = 0
+            page_size = 500
+            while True:
+                params = {
+                    'type': 'alphabeticalByArtist',
+                    'size': page_size,
+                    'offset': offset,
+                    'musicFolderId': self.music_folder_id
+                }
+                response = self._make_request('getAlbumList2', params)
+                if not response:
+                    break
+                album_list = response.get('albumList2', {}).get('album', [])
+                if not album_list:
+                    break
+                for a in album_list:
+                    aid = a.get('id', '')
+                    if aid:
+                        album_ids.add(aid)
+                if len(album_list) < page_size:
+                    break
+                offset += page_size
+            self._folder_album_ids = album_ids
+            logger.info(f"Built music folder album index: {len(album_ids)} albums in selected folder")
+            return album_ids
+        except Exception as e:
+            logger.warning(f"Could not build music folder album index: {e}")
+            return None
+
     def get_recently_added_albums(self, limit: int = 400) -> List[NavidromeAlbum]:
         """Get recently added albums from Navidrome using getAlbumList2 sorted by newest"""
         if not self.ensure_connection():