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/tools/odoo_client.py

@@ -37,10 +37,11 @@ class OdooWriteError(Exception): pass
 
 
 class OdooClient:
-    def __init__(self, url, db, api_key, pg_dsn=None, pg_pool_min=2, pg_pool_max=10):
+    def __init__(self, url, db, api_key, user='__system__', pg_dsn=None, pg_pool_min=2, pg_pool_max=10):
         self._url = url.rstrip('/')
         self._db = db
         self._api_key = api_key
+        self._user = user
         self._pg_dsn = pg_dsn
         self._pg_pool_min = pg_pool_min
         self._pg_pool_max = pg_pool_max
@@ -77,7 +78,7 @@ class OdooClient:
             try:
                 uid = await self._xmlrpc_call(
                     self._common, 'authenticate',
-                    self._db, '__system__', self._api_key, {})
+                    self._db, self._user, self._api_key, {})
                 if not uid:
                     raise OdooAuthError('Authentication failed - check ODOO_API_KEY')
                 self._uid = uid