Fix Binance boot using OKX symbols after restart.

Startup ignored DB exchange choice and kept OKX ATM ids under a Binance health label, so option bid/ask stayed empty.

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

backend/app/strategy/session.py

@@ -330,10 +330,14 @@ set_gateway = set_session
 
 
 def bootstrap_session(settings: Settings | None = None) -> StrategySession:
-    """main 启动：创建交易所 + 策略会话。"""
+    """main 启动：创建交易所 + 策略会话。始终以 DB 覆盖后的 runtime 为准。"""
     from ..exchange.runtime import load_runtime_settings
 
-    s = settings or load_runtime_settings()
+    # 忽略裸 get_settings()：重启后必须跟 DB 里选的交易所一致
+    try:
+        s = load_runtime_settings()
+    except Exception:
+        s = settings or get_settings()
     ex = build_exchange(s)
     set_exchange(ex)
     sess = StrategySession(s, ex)