refactor(media): merge the two MediaStreamKind enums into one shared enum

lib/media declared two different enums named MediaStreamKind — a 4-value one in media_stream.dart and a 7-value one in media_file_info.dart — so any file importing both libraries silently picked one by import order.

media_stream.dart's enum now carries the full member set (image/data/lyric added before unknown; the original four ordinals are preserved) and media_file_info.dart re-exports it instead of declaring its own.

lib/media/media_file_info.dart

@@ -1,6 +1,9 @@
 import '../i18n/strings.g.dart';
 
 import '../utils/formatters.dart';
+import 'media_stream.dart' show MediaStreamKind;
+
+export 'media_stream.dart' show MediaStreamKind;
 
 /// Backend-neutral file-info payload rendered by `FileInfoBottomSheet`.
 ///
@@ -252,8 +255,6 @@ class MediaFileAttachment {
   const MediaFileAttachment({this.index, this.fileName, this.mimeType, this.codec});
 }
 
-enum MediaStreamKind { video, audio, subtitle, image, data, lyric, unknown }
-
 /// Colour/HDR classification of a video stream, normalised across backends.
 ///
 /// Jellyfin reports it directly (`VideoRangeType`); Plex is derived from the

lib/media/media_stream.dart

@@ -1,5 +1,5 @@
 /// Type of an embedded or sidecar stream within a media file.
-enum MediaStreamKind { video, audio, subtitle, unknown }
+enum MediaStreamKind { video, audio, subtitle, image, data, lyric, unknown }
 
 /// A single audio, video, or subtitle stream inside a media part.
 class MediaStream {