feat: add 'Ask' quality option, language auto-select, and m4a audio remux

- Add 'ask' option to audio/video quality settings (stored as '' in DB)
- Auto-select when both media type AND quality are set; show filtered
  format picker when quality is Ask
- Auto-skip language picker when user has a matching language preference
- Remux audio-only downloads to m4a instead of webm for Telegram compat
- Update README to document the new flow and m4a audio output

internal/handler/download.go

@@ -161,7 +161,27 @@ func (h *Handler) handleURLInput(ctx context.Context, chatID int64, text string,
 
 	prefs, prefErr := h.Repo.GetOrCreatePreferences(userID)
 	if prefErr == nil && prefs.DefaultMediaType != domain.MediaTypeAsk {
-		h.autoSelectAndDownload(ctx, chatID, userID, url, info, prefs)
+		// Media type is set — check quality preference
+		var qualityPref string
+		switch prefs.DefaultMediaType {
+		case domain.MediaTypeVideo:
+			qualityPref = prefs.DefaultVideoFormat
+		case domain.MediaTypeAudio:
+			qualityPref = prefs.DefaultAudioFormat
+		}
+		if qualityPref != "" {
+			h.autoSelectAndDownload(ctx, chatID, userID, url, info, prefs)
+			return
+		}
+		// Quality is Ask — show filtered format picker
+		ss := &stepState{
+			URL:       url,
+			MediaInfo: info,
+			Step:      0,
+			CreatedAt: time.Now(),
+		}
+		h.setUserStepState(chatID, ss)
+		h.showFormatsForType(ctx, chatID, userID, ss, prefs.DefaultMediaType.String())
 		return
 	}
 
@@ -239,6 +259,34 @@ func (h *Handler) autoSelectAndDownload(ctx context.Context, chatID int64, userI
 	h.advanceToLanguage(ctx, chatID, msgID, userID, ss)
 }
 
+// showFormatsForType sends the format picker filtered by the given media type.
+// Called when the user has a type preference but quality is Ask.
+func (h *Handler) showFormatsForType(ctx context.Context, chatID int64, userID int64, ss *stepState, mediaType string) {
+	ids, err := buildFilteredFormatList(ss.MediaInfo.Formats, mediaType)
+	if err != nil {
+		h.sendText(ctx, chatID, "No formats available.")
+		return
+	}
+	ss.FormatIDs = ids
+	h.setUserStepState(chatID, ss)
+
+	labels := make([]string, len(ids))
+	for i, id := range ids {
+		if id == "best" {
+			labels[i] = "Best"
+		} else {
+			f := findFormatByID(ss.MediaInfo.Formats, id)
+			if f != nil {
+				labels[i] = formatLabelForDisplay(*f)
+			} else {
+				labels[i] = id
+			}
+		}
+	}
+	kb := formatKeyboard("format_", labels, ids)
+	h.sendWithKB(ctx, chatID, "Select format:", kb)
+}
+
 // handleTypeSelection processes the initial type picker (Video/Audio/Ask).
 func (h *Handler) handleTypeSelection(ctx context.Context, chatID int64, msgID int, userID int64, mediaType string) {
 	ss := h.getUserStepState(chatID)
@@ -394,6 +442,18 @@ func (h *Handler) advanceToLanguage(ctx context.Context, chatID int64, msgID int
 	h.setUserStepState(chatID, ss)
 
 	if len(ss.MediaInfo.Languages) > 1 {
+		// Check if user has a default language and it's available.
+		prefs, prefErr := h.Repo.GetOrCreatePreferences(userID)
+		if prefErr == nil && prefs.DefaultLanguage != "" {
+			for _, lang := range ss.MediaInfo.Languages {
+				if lang == prefs.DefaultLanguage {
+					ss.Language = lang
+					h.startDownload(ctx, chatID, msgID, userID, ss)
+					return
+				}
+			}
+		}
+		// No match or no preference — show picker.
 		kb := languageKeyboard(ss.MediaInfo.Languages)
 		h.editText(ctx, chatID, msgID, "Select language:", &kb)
 		return