Audit fixes: LIVE symbols/fills/expiry/pending, security harden, add 更新说明.

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

backend/app/api/settings.py

@@ -215,6 +215,7 @@ async def put_strategy_settings(
 class RuntimeSettingsBody(BaseModel):
     mode: Literal["SIM", "LIVE"] | None = None
     confirm_live: bool | None = False
+    confirm_live_phrase: str | None = None
     okx_api_key: str | None = None
     okx_api_secret: str | None = None
     okx_api_passphrase: str | None = None
@@ -272,6 +273,12 @@ async def put_runtime_settings(
                 status_code=400,
                 detail="切换到 LIVE 须二次确认（confirm_live=true）",
             )
+        phrase = (body.confirm_live_phrase or "").strip()
+        if phrase != "LIVE":
+            raise HTTPException(
+                status_code=400,
+                detail="切换到 LIVE 须在 confirm_live_phrase 传入 LIVE",
+            )
 
     updates: dict[str, str] = {}
     if body.okx_api_key is not None and body.okx_api_key.strip():