refactor: modularize IMAP server with fixes and E2E tests
- Modularize IMAP server into imap_server, imap_mailbox, imap_message,
imap_http_client, parse_email, config, models
- Support dual login: JWT token and address+password via backend
- Add STARTTLS support with configurable TLS cert/key
- Fix FETCH/STORE returning UID instead of sequence number (RFC 3501)
- Implement IMessageFile.open() for correct BODY[] raw MIME delivery
- Add UIDNEXT to SELECT response via _cbSelectWork override
- Use per-restart UIDVALIDITY to force client resync
- Pass raw MIME to SimpleMessage for accurate RFC822.SIZE
- Fix SENT mailbox returning empty source
- Handle CREATE command gracefully for Thunderbird compatibility
- Add IMAP E2E tests: auth, LIST, SELECT, STATUS, FETCH, SEARCH,
STORE, UID FETCH, BODY[] integrity, size, seq numbers, SENT mailbox
- Add SMTP E2E tests using nodemailer: send plain/HTML, auth failure,
sendbox verification
- Add sendTestMail helper using admin/send_mail
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
