feat: 计仓改为固定手数/固定金额，推荐过滤与CTP保证金，下单与持仓UI优化

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

vnpy_bridge.py

@@ -789,6 +789,28 @@ class CtpBridge:
     def _lookup_position_margin(self, sym: str, direction: str) -> float:
         return float(self._position_margins.get(self._position_margin_key(sym, direction), 0) or 0)
 
+    def estimate_margin_one_lot(self, ths_code: str, price: float) -> Optional[float]:
+        """用 CTP 合约信息估算 1 手保证金（需已连接并完成合约查询）。"""
+        if not self._engine or not price or price <= 0:
+            return None
+        try:
+            sym, ex_name = ths_to_vnpy_symbol(ths_code)
+            exchange = to_vnpy_exchange(ex_name)
+            vt_symbol = f"{sym}.{exchange.value}"
+            contract = self._engine.get_contract(vt_symbol)
+            if not contract:
+                return None
+            mult = float(getattr(contract, "size", 0) or 0)
+            long_r = float(getattr(contract, "long_margin_ratio", 0) or 0)
+            short_r = float(getattr(contract, "short_margin_ratio", 0) or 0)
+            ratio = max(long_r, short_r)
+            if mult <= 0 or ratio <= 0:
+                return None
+            return round(float(price) * mult * ratio, 2)
+        except Exception as exc:
+            logger.debug("estimate_margin_one_lot %s: %s", ths_code, exc)
+            return None
+
     def _collect_positions(self) -> list[dict[str, Any]]:
         if not self._engine:
             return []
@@ -1074,6 +1096,17 @@ def ctp_get_tick_detail(mode: str, ths_code: str) -> dict[str, Any]:
         return {}
 
 
+def ctp_estimate_margin_one_lot(mode: str, ths_code: str, price: float) -> Optional[float]:
+    b = get_bridge()
+    if b.connected_mode != mode or not b.ping():
+        return None
+    try:
+        return b.estimate_margin_one_lot(ths_code, price)
+    except Exception as exc:
+        logger.debug("ctp_estimate_margin_one_lot: %s", exc)
+        return None
+
+
 def get_ctp_balance(mode: str) -> Optional[float]:
     try:
         acc = ctp_get_account(mode)