refactor: redesign format selection with unified list and independent audio/video picking

- Replace type/quality selection flow with unified format list (video+audio combined)
- Add independent audio/video format picking: video-only formats prompt for audio track,
  audio-only formats offer optional video addition (skip when content is audio-only)
- Fix formatKeyboard to use format IDs as callback data instead of display labels
- Remove dead mediaTypeKeyboard function
- Fix double-close panic in readProgress (caller is sole owner of updates channel)
- Add FormatString field to DownloadJob for composite format specs (e.g. '137+140')
- Change quota calculation from sum of all format sizes to max single format size
- Fix 'Delete all data' button to use danger style with proper text
- Clean up routePrefixedCallback: remove type_/quality_, add format_/secondary_ routes
- Fix back navigation to rebuild format IDs list

internal/handler/settings.go

@@ -41,7 +41,7 @@ func (h *Handler) buildSettingsKeyboard(userID int64, prefs *domain.UserPreferen
 			{Text: fmt.Sprintf("Container: %s", containerLabel), CallbackData: "settings_container"},
 			{Text: fmt.Sprintf("Language: %s", langLabel), CallbackData: "settings_language"},
 		},
-		{{Text: "Delete my data", CallbackData: "delaccount_prompt"}},
+		{{Text: "Delete all data", CallbackData: "deleteaccount", Style: "danger"}},
 		{{Text: "Back to Menu", CallbackData: "back_menu"}},
 	}
 	return "Settings:", models.InlineKeyboardMarkup{InlineKeyboard: rows}
@@ -232,7 +232,7 @@ func (h *Handler) handleSettingsSet(ctx context.Context, chatID int64, msgID int
 // deleteAccountPrompt shows the deletion confirmation prompt.
 func (h *Handler) deleteAccountPrompt(ctx context.Context, chatID int64, msgID int, userID int64) {
 	kb := deleteConfirmKeyboard(userID)
-	h.editText(ctx, chatID, msgID, "This will permanently delete ALL your data (preferences, quota, history).\nAre you sure?", &kb)
+	h.editText(ctx, chatID, msgID, "This will permanently delete ALL your data (preferences, quotas, history).\nAre you sure?", &kb)
 }
 
 // deleteAccountConfirm permanently deletes all user data.