Align margin display with CTP counter rates and position margin.

Read margin ratios from CTP instrument query and margin-rate API instead of vnpy ContractData (which lacks ratios). Keep occupied margin on position UseMargin; use per-lot max rate for recommend table.

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

contract_specs.py

@@ -92,6 +92,7 @@ def margin_one_lot(
 ) -> tuple[float, str, dict]:
     """1 手保证金。CTP 已连接时优先读柜台合约保证金率，否则用本地参考规格估算。
 
+    direction 可为 long / short / max（多空费率取较大值，用于可开仓品种表）。
     返回 (保证金, 来源 estimate|ctp, 合约规格片段)。
     """
     spec = get_contract_spec(ths_code)
@@ -113,6 +114,8 @@ def margin_one_lot(
                         merged["mult"] = ctp_spec["mult"]
                     if ctp_spec.get("tick_size"):
                         merged["tick_size"] = ctp_spec["tick_size"]
+                    if ctp_spec.get("margin_rate"):
+                        merged["margin_rate"] = ctp_spec["margin_rate"]
                     return float(ctp_margin), "ctp", merged
         except Exception:
             pass