fix(broker): enforce operator broker truth boundary

trex_core/adapters/persistence/postgresql.py

@@ -134,6 +134,18 @@ class PostgreSQLSlotRepository:
                 )
                 return [self._row_to_slot(r) for r in cur.fetchall()]
 
+    def find_managed_slot_by_symbol(self, instance_key: str, symbol: str) -> Optional[Slot]:
+        with self._psycopg.connect(self._dsn) as conn:
+            with conn.cursor() as cur:
+                cur.execute(
+                    f"SELECT {_SLOT_COLUMNS} FROM daily_slot "
+                    "WHERE instance_key = %s AND symbol = %s "
+                    "ORDER BY updated_at DESC NULLS LAST, slot_id ASC LIMIT 1",
+                    (instance_key, symbol),
+                )
+                row = cur.fetchone()
+                return self._row_to_slot(row) if row else None
+
     def reconcile_universe(
         self, instance_key: str, universe: dict[str, str],
         *, allow_retire: bool = True,