Create And Bind

Atomically create a new workspace and bind this project to it.

Single handler-owned transaction: the Datamate row and the binding row either both commit or both roll back. A partial-unique-index conflict on the binding (the identifier is already bound to another workspace for this tenant) 409s with the winning workspace's {id, name} so the CLI can prompt "re-link?" — no orphan Datamate is left behind.

cache.clear() fires post-commit so the caller's GET /datamates/ sees the new workspace within one request instead of waiting up to five minutes for the TTL cache to expire.