- Created a CI workflow in `.github/workflows/ci.yml` to run Go tests and verify database migrations.
- Added unit tests for the mail API in `internal/api/mail/handlers_test.go`, covering message listing, retrieval, sending, and label updating.
- Introduced a service interface for the mail handler in `internal/api/mail/service_iface.go`.
- Updated mail handler initialization to accept a service API in `internal/api/mail/handlers.go`.
- Implemented test authentication middleware for testing purposes in `internal/api/middleware/testauth.go`.
- Added various test cases for IMAP and SMTP functionalities, ensuring robust error handling and validation.
- Enhanced project documentation with checklist updates for testing and CI integration.
