GHSA-wjjj-24cx-f28g: SurrealDB has unauthenticated remote DoS via malformed RPC `use` call

A single unauthenticated WebSocket message to /rpc crashed the SurrealDB server. Sending use { db: "x" } without first selecting a namespace hit .expect("namespace should be set") in the use handler; because surrealdb-core is built with panic = 'abort', the panic terminated the process. use is callable before signin, and the per-method capability check passes by default for guest callers — so no credentials, token, or --allow-guests flag are required.