refactor: settings format picker redesign with Audio/Video sub-pickers, fix delete routing

- Replace Type/Quality settings with single Format button -> Audio/Video sub-pickers
- Each sub-picker shows format options (bitrates for audio, resolutions for video)
- Replace DefaultQuality with DefaultAudioFormat/DefaultVideoFormat in UserPreferences
- Add DB migration 002 for new preference columns
- Update repo layer SQL queries for new schema
- Update playlist flow to use new preference fields
- Fix missing deleteaccount and delaccount_ callback routing
- Add back_format routing for format picker navigation

internal/handler/playlist.go

@@ -142,15 +142,20 @@ func (h *Handler) handlePlaylistConfirm(ctx context.Context, chatID int64, msgID
 		prefs, prefErr := h.Repo.GetOrCreatePreferences(userID)
 		if prefErr != nil {
 			prefs = &domain.UserPreferences{
-				DefaultMediaType: domain.MediaTypeVideoAudio,
-				DefaultQuality:   "best",
-				DefaultContainer: "mp4",
+				DefaultMediaType:   domain.MediaTypeVideoAudio,
+				DefaultAudioFormat: "best",
+				DefaultVideoFormat: "best",
+				DefaultContainer:   "mp4",
 			}
 		}
 
-		format := &domain.Format{ID: prefs.DefaultQuality}
+		formatID := prefs.DefaultVideoFormat
+		if prefs.DefaultMediaType == domain.MediaTypeAudio {
+			formatID = prefs.DefaultAudioFormat
+		}
+		format := &domain.Format{ID: formatID}
 		for _, f := range info.Formats {
-			if f.ID == prefs.DefaultQuality {
+			if f.ID == formatID {
 				format = &f
 				break
 			}