The "database" target type now writes events to a separate
archived_events table instead of just marking the delivery as done.
This table persists independently of internal event retention/pruning,
allowing the data to be consumed by external systems or preserved
indefinitely.
New ArchivedEvent model copies the full event payload (method, headers,
body, content_type) along with webhook/entrypoint/event/target IDs.
Store the *database.Database wrapper instead of calling .DB() eagerly
at construction time. The GORM *gorm.DB is only available after the
database's OnStart hook runs, but the engine constructor runs during
fx resolution (before OnStart). Accessing .DB() lazily via the wrapper
avoids the nil pointer panic.