Pass the homeserver's RustRuntime from synapse_port_db

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ULdieJyQoHNzeHq42H2M1p

synapse/_scripts/synapse_port_db.py

@@ -664,6 +664,7 @@ class Porter:
             engine=engine,
             default_txn_name="portdb",
             server_name=server_name,
+            runtime=self.hs.get_rust_runtime(),
         ) as db_conn:
             engine.check_database(
                 db_conn, allow_outdated_version=allow_outdated_version