fix(agent): coerce user_id to int in MasterAgent.handle_message

Odoo's bot model serialises user_id as a string (str(uid)) over the
HTTP boundary, but the asyncpg memory queries ($1) expect an integer.
This caused 'str object cannot be interpreted as an integer' on every
Discuss DM. Cast at the entry point so downstream stores get an int.

agent_service/agents/master_agent.py

@@ -70,6 +70,10 @@ class MasterAgent:
         return template.format(agent_list=agent_list)
 
     async def handle_message(self, user_id, channel_id, message, directive_id) -> MasterResponse:
+        try:
+            user_id = int(user_id)
+        except (TypeError, ValueError):
+            pass
         logger.info('MasterAgent.handle_message user_id=%s directive=%s', user_id, directive_id)
         t0 = time.monotonic()
         await self._log_directive_start(directive_id, user_id, channel_id, message)