Add `created_at: Option<DateTime<Utc>>` through all layers so CLI users
can backdate entities at creation/update time. When omitted, falls back
to `Utc::now()`.
- Domain: add field to all New*/Update* structs with serde(default)
- Domain: timeline events use entity created_at instead of Utc::now()
- Repos: unify INSERT to explicit Rust-side created_at with unwrap_or_else
- Repos: add created_at to UPDATE dynamic query builders
- Routes: add field to submission structs and has_changes guards
- Clients: pass created_at through manual JSON client methods
- CLI: add --created-at flag with parse_created_at helper (RFC 3339 or YYYY-MM-DD)
Previously, list endpoints returned enriched types (RoastWithRoaster,
BagWithRoast) with related entity names, while get/create/update
endpoints returned bare types without this information.
This change makes all endpoints consistent by returning enriched types:
- Added get_with_roaster and get_with_roast repository methods
- Created define_enriched_get_handler! macro for custom getter methods
- Updated create and update handlers to fetch enriched data after write
- Updated CLI client to expect enriched types
