Fix server hang: stop CTP reconnect storm and throttle live account polling.

Co-authored-by: Cursor <cursoragent@cursor.com>

modules/trading/position_stream.py

@@ -45,6 +45,12 @@ class PositionStreamHub:
         with self._lock:
             return dict(self._snapshot) if self._snapshot else None
 
+    def snapshot_age_sec(self) -> float:
+        with self._lock:
+            if not self._snapshot_ts:
+                return 9999.0
+            return max(0.0, time.time() - self._snapshot_ts)
+
     def set_snapshot(self, data: dict) -> None:
         with self._lock:
             self._snapshot = dict(data)