feat(music): offer File Info on tracks and other file-backed items

The context menu only offered File Info for movies and episodes, so a
track's path, container, and audio stream detail were unreachable even
though both backends already answer getFileInfo for them.

Gate the entry on the new MediaKind.hasFileInfo instead of a literal
kind list: movies, episodes, tracks, and clips are leaf items with real
files, while shows, seasons, artists, albums, collections, playlists,
and folders carry no Media/MediaSources and would only ever produce the
"not available" snackbar.

Also fix the Plex stream classifier, which mapped streamType 4 to an
embedded image although PlexStreamType.lyrics is 4. Only music tracks
carry that type, so a track's lyric stream rendered under "Embedded
Images" with the video field block. Type 5 was invented outright and is
now unknown.

close #1747

lib/widgets/media_context_menu.dart

@@ -546,12 +546,15 @@ class MediaContextMenuState extends State<MediaContextMenu> {
         );
       }
 
-      // File Info (for episodes and movies). Backend-neutral — both
-      // PlexClient and JellyfinClient implement [getFileInfo], reading
-      // codec/stream metadata from `Media`/`MediaSources` respectively.
-      // Hidden when the item has no backend marker so we don't fan out
-      // to an arbitrary client.
-      if (itemBackend != null && (mediaKind == MediaKind.episode || mediaKind == MediaKind.movie)) {
+      // File Info — every file-backed leaf kind (movies, episodes, tracks,
+      // clips). Backend-neutral: both PlexClient and JellyfinClient implement
+      // [MediaServerClient.getFileInfo], reading codec/stream metadata from
+      // `Media`/`MediaSources` respectively. Container kinds are excluded by
+      // [MediaKind.hasFileInfo] because neither backend attaches media sources
+      // to them — a show/season/album/artist entry would only ever produce the
+      // "not available" snackbar. Hidden when the item has no backend marker
+      // so we don't fan out to an arbitrary client.
+      if (itemBackend != null && mediaKind != null && mediaKind.hasFileInfo) {
         menuActions.add(_MenuAction(value: 'fileinfo', icon: Symbols.info_rounded, label: t.mediaMenu.fileInfo));
       }