Add Binance SIM market adapter and exchange switch in settings.

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

backend/app/strategy/session.py

@@ -286,7 +286,10 @@ class StrategySession:
         return self.ex.snapshot(self.settings.perp_inst_id)
 
     def snapshot_dict(self) -> dict[str, Any]:
-        return self.ex.snapshot_dict(self.settings.perp_inst_id)
+        d = self.ex.snapshot_dict(self.settings.perp_inst_id)
+        d["exchange"] = getattr(self.ex, "name", self.settings.exchange)
+        d["perp_inst_id"] = self.settings.perp_inst_id
+        return d
 
     async def _refresh_loop(self) -> None:
         while True:
@@ -328,7 +331,9 @@ set_gateway = set_session
 
 def bootstrap_session(settings: Settings | None = None) -> StrategySession:
     """main 启动：创建交易所 + 策略会话。"""
-    s = settings or get_settings()
+    from ..exchange.runtime import load_runtime_settings
+
+    s = settings or load_runtime_settings()
     ex = build_exchange(s)
     set_exchange(ex)
     sess = StrategySession(s, ex)