fix: permission error message and Android 13+ storage permission

- Fixed download showing 'Song not found' when actually permission error
- Added permission error type detection in Go backend
- Android 13+ now requests both MANAGE_EXTERNAL_STORAGE and READ_MEDIA_AUDIO
- MANAGE_EXTERNAL_STORAGE opens Settings (system-level)
- READ_MEDIA_AUDIO shows dialog (app-level, resets on clear data)
- Proper permission check before showing 'granted' status

go_backend/exports.go

@@ -991,6 +991,12 @@ func errorResponse(msg string) (string, error) {
 		strings.Contains(lowerMsg, "try using vpn") ||
 		strings.Contains(lowerMsg, "change dns") {
 		errorType = "isp_blocked"
+	} else if strings.Contains(lowerMsg, "permission") ||
+		strings.Contains(lowerMsg, "operation not permitted") ||
+		strings.Contains(lowerMsg, "access denied") ||
+		strings.Contains(lowerMsg, "failed to create file") ||
+		strings.Contains(lowerMsg, "failed to create directory") {
+		errorType = "permission"
 	} else if strings.Contains(lowerMsg, "not found") ||
 		strings.Contains(lowerMsg, "not available") ||
 		strings.Contains(lowerMsg, "no results") ||