Catch GrammyError when getFile fails for files >20MB (Telegram Bot API limit).
Log warning, skip attachment, but continue processing message text.
- Add FILE_TOO_BIG_RE regex to detect 'file is too big' errors
- Add isFileTooBigError() and isRetryableGetFileError() helpers
- Skip retrying permanent 400 errors (they'll fail every time)
- Log specific warning for file size limit errors
- Return null so message text is still processed
Fixes#18518
01b37f1d32