- New src/retry.py with configurable retry decorator
- Applied @retry() to fetch_unseen_emails, mark_as_seen,
summarize_email, and send_message
- No backoff delay between retries
These providers require a client identification (ID command, RFC 2971)
before SELECT INBOX, otherwise they reject with 'SELECT Unsafe Login'.
Extract shared login+select logic into _login_and_prepare helper.
- Add _select_mailbox helper that raises on non-OK status
- Prevents 'command SEARCH illegal in state AUTH' by catching
failed mailbox selection early with a clear error message
