Add Binance SIM market adapter and exchange switch in settings.

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

backend/app/exchange/runtime.py

@@ -0,0 +1,86 @@
+"""运行时交易所配置：DB 覆盖 env，切换时套用合约默认。"""
+
+from __future__ import annotations
+
+from ..config import EXCHANGE_MARKET_DEFAULTS, Settings, get_settings
+
+
+def normalize_exchange_name(name: str | None) -> str:
+    n = (name or "okx").strip().lower()
+    if n in ("bn", "binance"):
+        return "binance"
+    return "okx"
+
+
+def load_runtime_settings() -> Settings:
+    """启动 / 切换后使用的有效 Settings（含 DB 覆盖）。"""
+    base = get_settings()
+    try:
+        from ..models.db import get_db
+
+        db = get_db()
+    except Exception:
+        return base
+
+    ex = normalize_exchange_name(db.get_setting("exchange", base.exchange))
+    defs = EXCHANGE_MARKET_DEFAULTS[ex]
+    ct_default = float(defs["option_ct_mult_default"])
+    raw_ct = db.get_setting("option_ct_mult_default")
+    if raw_ct not in (None, ""):
+        try:
+            ct_default = float(raw_ct)
+        except ValueError:
+            pass
+    return base.model_copy(
+        update={
+            "exchange": ex,
+            "perp_inst_id": str(
+                db.get_setting("perp_inst_id") or defs["perp_inst_id"]
+            ),
+            "option_inst_family": str(
+                db.get_setting("option_inst_family") or defs["option_inst_family"]
+            ),
+            "index_inst_id": str(
+                db.get_setting("index_inst_id") or defs["index_inst_id"]
+            ),
+            "option_ct_mult_default": ct_default,
+        }
+    )
+
+
+def persist_exchange_choice(name: str) -> Settings:
+    """写入 exchange + 该所合约默认，返回 runtime settings。"""
+    from ..models.db import get_db
+
+    ex = normalize_exchange_name(name)
+    defs = EXCHANGE_MARKET_DEFAULTS[ex]
+    db = get_db()
+    db.set_setting("exchange", ex)
+    db.set_setting("perp_inst_id", str(defs["perp_inst_id"]))
+    db.set_setting("option_inst_family", str(defs["option_inst_family"]))
+    db.set_setting("index_inst_id", str(defs["index_inst_id"]))
+    db.set_setting("option_ct_mult_default", str(defs["option_ct_mult_default"]))
+    return load_runtime_settings()
+
+
+async def reload_market_session(settings: Settings | None = None):
+    """停旧会话、按 settings 重建交易所与策略会话并 start。"""
+    from .factory import set_exchange
+    from ..strategy.session import bootstrap_session, get_session, set_session
+
+    s = settings or load_runtime_settings()
+    old = None
+    try:
+        old = get_session()
+    except Exception:
+        old = None
+    if old is not None:
+        try:
+            await old.stop()
+        except Exception:
+            pass
+    set_session(None)
+    set_exchange(None)
+    sess = bootstrap_session(s)
+    await sess.start()
+    return sess