feat(upload): enhance audio upload handling and user feedback

- Introduced a new warning for users uploading non-FLAC or WAV formats, indicating that these formats should only be used as a last resort.
- Added functionality to highlight files needing format attention in the upload queue.
- Updated the UI to provide clearer guidance on acceptable audio formats during uploads.
- Improved documentation to reflect changes in upload requirements and user interface updates.

packages/i18n/locales/en/admin.json

@@ -200,7 +200,9 @@
     "suggest_title": "Suggest tracks",
     "suggest_subtitle": "Files go to the upload queue; an administrator reviews them and places them into a storage",
     "drop_title": "Drop music files or folders here",
-    "drop_hint": "Formats: {{formats}}. Folder structure helps guess the artist and album.",
+    "drop_hint": "Use FLAC or WAV. MP3 only as a last resort: the quality is worse, and the queue marks that file “needs attention”.",
+    "drop_folders": "Folder structure helps guess the artist and album.",
+    "format_attention": "Not FLAC or WAV. Send MP3 only when there is no lossless file.",
     "pick_files": "Choose files",
     "pick_folder": "Choose folder",
     "files": "Files to send",
@@ -286,6 +288,7 @@
     "edited": "edited",
     "flag_possible": "possible duplicate",
     "flag_quality": "better quality",
+    "flag_attention": "needs attention",
     "listen": "Listen to {{name}}",
     "edit_batch": "Whole batch",
     "batch_edit_title": "Edit batch",