feat: add retry(10) on all network requests

- 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

src/email_client.py

@@ -4,6 +4,7 @@ from email.header import decode_header
 from email.utils import parsedate_to_datetime
 from typing import Optional
 from src.config import EmailAccount
+from src.retry import retry
 
 
 class Email:
@@ -76,6 +77,7 @@ def _login_and_prepare(account: EmailAccount):
     return conn
 
 
+@retry()
 def fetch_unseen_emails(account: EmailAccount) -> list[Email]:
     conn = _login_and_prepare(account)
 
@@ -101,6 +103,7 @@ def fetch_unseen_emails(account: EmailAccount) -> list[Email]:
     return emails
 
 
+@retry()
 def mark_as_seen(account: EmailAccount, uids: list[bytes]):
     if not uids:
         return