Use-after-free in KV backends via leaked affinitypool::spawn_local future

SurrealDB before 3.3.0 contains a use-after-free vulnerability in surrealdb-core KV backends that pass borrowed transaction state into affinitypool::spawn_local closures relying on future Drop for safety. Rust embedders that leak a dispatched future (e.g. via mem::forget) and drop the transaction cause pool workers to read and write freed memory, risking crashes or memory corruption.