fix(authz): handle async gRPC UnaryUnaryCall responses

authzed Client returns UnaryUnaryCall futures, not direct responses.
Call .result() to resolve the future before accessing attributes.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ImTotem

src/bcsd_api/authz/client.py

@@ -47,13 +47,14 @@ def __init__(self, endpoint: str, token: str):
         )
 
     def check(self, res_type: str, res_id: str, permission: str, user_id: str) -> bool:
-        resp = self._client.CheckPermission(
+        call = self._client.CheckPermission(
             CheckPermissionRequest(
                 resource=_object_ref(res_type, res_id),
                 permission=permission,
                 subject=_subject_ref(user_id),
             )
         )
+        resp = call.result() if hasattr(call, "result") else call
         return resp.permissionship == _HAS
 
     def add_relation(self, res_type: str, res_id: str, relation: str, user_id: str) -> None:
@@ -63,9 +64,13 @@ def remove_relation(self, res_type: str, res_id: str, relation: str, user_id: st
         self._write(_DELETE, res_type, res_id, relation, user_id)
 
     def write_schema(self, schema: str) -> None:
-        self._client.WriteSchema(WriteSchemaRequest(schema=schema))
+        call = self._client.WriteSchema(WriteSchemaRequest(schema=schema))
+        if hasattr(call, "result"):
+            call.result()
 
     def _write(self, operation: int, res_type: str, res_id: str, relation: str, user_id: str) -> None:
-        self._client.WriteRelationships(
+        call = self._client.WriteRelationships(
             WriteRelationshipsRequest(updates=[_update(operation, res_type, res_id, relation, user_id)])
         )
+        if hasattr(call, "result"):
+            call.result()