Release Notes 0.6.09.031531

- Initial MVP `novij-mail-service`: health/version/status, mailbox management, IMAP sync, attachment metadata, Actions dispatch, send queue, and `.deb` package flow.

- Switched the default Relay from retiring Hinata/Ino to Relay SPB and added safe migration for existing configuration.

- Production CI smoke now fails when live-host access is not configured.

- Mailboxes in the `degraded` state now take part in scheduled and manual synchronization retries and return to `active` after a successful attempt.

- Message previews are now truncated on a UTF-8 character boundary and no longer produce invalid PostgreSQL input.