- Added ImapSynchronizerMailio using mailio library (C++17, Boost)
- CMake option USE_MAILIO_IMAP (OFF by default) to avoid Boost dependency
- Fetches Boost + mailio via FetchContent when enabled
- Implements full IMAP: connect, auth (LOGIN/XOAUTH2), LIST, SELECT, FETCH, STORE, APPEND, EXPUNGE
- SyncFolder: detects deletions, fetches new messages, updates flags in batches
- XOAUTH2 support for Gmail/Outlook OAuth2 tokens
- Falls back to original ImapSynchronizer when USE_MAILIO_IMAP=OFF
- Ready to enable with: cmake -DUSE_MAILIO_IMAP=ON
javier
f798f7ecc0