For JMAP accounts, setFlag/moveEmail/deleteEmail now write to the
pending_changes table instead of making direct server calls, enabling
offline-first mutation with durable retries.
flushPendingChanges() drains the queue at the start of each JMAP
sync cycle via Email/set (flag updates use keyword patches; move
updates mailboxIds; delete uses Email/set destroy). On failure the
attempt count and last error are recorded; the change remains queued.
Local DB is updated optimistically on mutation so the UI responds
immediately.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
