fix: transcode IVR audio uploads to OGG/Opus 48kHz mono

Apply the same ffmpeg transcoding to UploadIVRAudio that was added to
UploadOrgAudio, so IVR greeting audio files are also guaranteed to be
compatible with the WebRTC AudioPlayer.

Author: shridarpatil

internal/handlers/ivr_flows.go

@@ -336,30 +336,36 @@ func (a *App) UploadIVRAudio(r *fastglue.Request) error {
 		return r.SendErrorEnvelope(fasthttp.StatusBadRequest, "Unsupported audio type: "+mimeType, nil, "")
 	}
 
-	// Determine extension
-	ext := getExtensionFromMimeType(mimeType)
-	if ext == "" {
-		ext = ".bin"
-	}
-
 	// Ensure audio directory exists
 	audioDir := a.getAudioDir()
 	if err := os.MkdirAll(audioDir, 0755); err != nil {
 		a.Log.Error("Failed to create audio directory", "error", err)
 		return r.SendErrorEnvelope(fasthttp.StatusInternalServerError, "Failed to create audio directory", nil, "")
 	}
 
-	// Generate filename: uuid + extension
-	filename := uuid.New().String() + ext
+	// Save uploaded file to a temp location for transcoding
+	tmpInput, err := os.CreateTemp("", "ivr-audio-input-*")
+	if err != nil {
+		return r.SendErrorEnvelope(fasthttp.StatusInternalServerError, "Failed to create temp file", nil, "")
+	}
+	defer os.Remove(tmpInput.Name())
+
+	if _, err := tmpInput.Write(data); err != nil {
+		tmpInput.Close()
+		return r.SendErrorEnvelope(fasthttp.StatusInternalServerError, "Failed to write temp file", nil, "")
+	}
+	tmpInput.Close()
+
+	// Transcode to OGG/Opus 48kHz mono for WebRTC compatibility
+	filename := uuid.New().String() + ".ogg"
 	filePath := filepath.Join(audioDir, filename)
 
-	// Save file
-	if err := os.WriteFile(filePath, data, 0644); err != nil {
-		a.Log.Error("Failed to save audio file", "error", err)
-		return r.SendErrorEnvelope(fasthttp.StatusInternalServerError, "Failed to save audio file", nil, "")
+	if err := transcodeToOpus(tmpInput.Name(), filePath); err != nil {
+		a.Log.Error("IVR audio transcoding failed", "error", err, "original_mime", mimeType)
+		return r.SendErrorEnvelope(fasthttp.StatusInternalServerError, "Failed to transcode audio to Opus format", nil, "")
 	}
 
-	a.Log.Info("IVR audio uploaded", "filename", filename, "mime_type", mimeType, "size", len(data))
+	a.Log.Info("IVR audio uploaded", "filename", filename, "original_mime", mimeType, "size", len(data))
 
 	return r.SendEnvelope(map[string]any{
 		"filename":  filename,