fix: make Odoo login configurable via ODOO_USER (default __system__)

Some Odoo instances require the user's actual login/email for API key
auth rather than the __system__ special login. ODOO_USER defaults to
__system__ for standard Odoo 16+ installs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

agent_service/main.py

@@ -85,6 +85,7 @@ async def lifespan(app: FastAPI):
             url=settings.odoo_url,
             db=settings.odoo_db,
             api_key=settings.odoo_api_key,
+            user=settings.odoo_user,
         )
         logger.info('Odoo client initialised (%s)', settings.odoo_url)
     except Exception as exc: