Partitioned order IDs

Business order IDs now use UUIDv7 while legacy numeric IDs remain accepted for compatibility.

Business order responses now return the canonical order primary key as a
UUIDv7 string after the partitioned orders-table migration. Use the response
id for follow-up business API calls such as GET /v3/orders/{id} and
PATCH /v3/orders/{id}. Legacy numeric order IDs for migrated orders remain
accepted on ID routes and bulk ids payloads for compatibility.