feat(cryptotail): 尾盘监控双连接与分时图优化

- 监控 WebSocket 拆分为当前周期连接与下一周期连接，周期切换时关闭过期连接并新建下一周期
- 下一周期市场未创建时也建立第二条空连接，保证始终两条连接
- refreshSubscription 增加 Mutex 防重入，避免周期结束时定时器与消息同时触发导致重复执行
- 修复 initMonitor/buildPushData 中 getCurrentOpenClose、spreadMode/spreadValue 等 API 与实体字段引用
- 移除重复的 buildSubscriptionMap、buildPushData 等方法，修复 StrategyPriceData.periodStartUnix
- 前端分时图：市场价折线增加 connectNulls，新周期默认 0.5 价格展示
- 多语言与监控页入口、API 类型与 WebSocket 订阅集成

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

frontend/src/locales/en/common.json

@@ -313,6 +313,7 @@
     "templates": "Templates",
     "copyTradingConfig": "Copy Trading Config",
     "cryptoTailStrategy": "Tail Strategy",
+    "cryptoTailMonitor": "Tail Monitor",
     "positions": "Position Management",
     "backtest": "Backtest",
     "statistics": "Statistics",
@@ -1541,5 +1542,57 @@
       "emptyFail": "No failed records",
       "totalCount": "{count} record(s)"
     }
+  },
+  "cryptoTailMonitor": {
+    "title": "Tail Strategy Monitor",
+    "selectStrategy": "Strategy",
+    "selectStrategyPlaceholder": "Select a strategy to monitor",
+    "direction": "Direction",
+    "directionUp": "Up",
+    "directionDown": "Down",
+    "noData": "Select a strategy to start monitoring",
+    "priceRange": "Price Range",
+    "timeWindow": "Time Window",
+    "stat": {
+      "openPrice": "Open Price",
+      "currentPrice": "Current Price",
+      "spread": "Spread",
+      "remainingTime": "Remaining",
+      "configuredSpread": "Configured Spread",
+      "configuredSpreadMin": "Min Spread",
+      "configuredSpreadMax": "Max Spread",
+      "status": "Status",
+      "minSpreadLine": "Min Spread",
+      "periodSpreadMinMax": "Period Spread",
+      "periodSpreadMin": "Period Min Spread",
+      "periodSpreadMax": "Period Max Spread",
+      "minSpread": "Min",
+      "maxSpread": "Max"
+    },
+    "status": {
+      "triggered": "Triggered",
+      "periodEnded": "Period Ended",
+      "inCondition": "In Condition",
+      "waiting": "Waiting"
+    },
+    "chart": {
+      "title": "Price Chart",
+      "btcTitle": "BTC Price Chart",
+      "marketTitle": "Market Price Chart",
+      "price": "BTC Price",
+      "openPrice": "Open",
+      "spread": "Spread",
+      "minSpreadLine": "Min Spread Line",
+      "marketUp": "Up",
+      "marketDown": "Down",
+      "time": "Time"
+    },
+    "strategyInfo": {
+      "title": "Strategy Info",
+      "market": "Market",
+      "interval": "Interval",
+      "account": "Account",
+      "spreadMode": "Spread Mode"
+    }
   }
 }

frontend/src/locales/zh-CN/common.json

@@ -312,6 +312,7 @@
     "templates": "跟单模板",
     "copyTradingConfig": "跟单配置",
     "cryptoTailStrategy": "尾盘策略",
+    "cryptoTailMonitor": "尾盘监控",
     "positions": "仓位管理",
     "backtest": "回测",
     "statistics": "统计信息",
@@ -1540,5 +1541,57 @@
       "emptyFail": "暂无失败记录",
       "totalCount": "共 {count} 条"
     }
+  },
+  "cryptoTailMonitor": {
+    "title": "尾盘策略监控",
+    "selectStrategy": "选择策略",
+    "selectStrategyPlaceholder": "请选择要监控的策略",
+    "direction": "监控方向",
+    "directionUp": "Up",
+    "directionDown": "Down",
+    "noData": "请选择一个策略开始监控",
+    "priceRange": "价格区间",
+    "timeWindow": "时间窗口",
+    "stat": {
+      "openPrice": "开盘价",
+      "currentPrice": "最新价",
+      "spread": "价差",
+      "remainingTime": "剩余时间",
+      "configuredSpread": "配置价差",
+      "configuredSpreadMin": "最小价差",
+      "configuredSpreadMax": "最大价差",
+      "status": "状态",
+      "minSpreadLine": "最小价差线",
+      "periodSpreadMinMax": "周期内价差",
+      "periodSpreadMin": "周期内最小价差",
+      "periodSpreadMax": "周期内最大价差",
+      "minSpread": "最小",
+      "maxSpread": "最大"
+    },
+    "status": {
+      "triggered": "已触发",
+      "periodEnded": "周期结束",
+      "inCondition": "满足条件",
+      "waiting": "等待中"
+    },
+    "chart": {
+      "title": "分时图",
+      "btcTitle": "BTC 分时图",
+      "marketTitle": "市场分时图",
+      "price": "BTC 价格",
+      "openPrice": "开盘价",
+      "spread": "价差",
+      "minSpreadLine": "最小价差线",
+      "marketUp": "Up",
+      "marketDown": "Down",
+      "time": "时间"
+    },
+    "strategyInfo": {
+      "title": "策略信息",
+      "market": "市场",
+      "interval": "周期",
+      "account": "账户",
+      "spreadMode": "价差模式"
+    }
   }
 }

frontend/src/locales/zh-TW/common.json

@@ -313,6 +313,7 @@
     "templates": "跟單模板",
     "copyTradingConfig": "跟單配置",
     "cryptoTailStrategy": "尾盤策略",
+    "cryptoTailMonitor": "尾盤監控",
     "positions": "倉位管理",
     "backtest": "回測",
     "statistics": "統計信息",
@@ -1541,5 +1542,57 @@
       "emptyFail": "暫無失敗記錄",
       "totalCount": "共 {count} 條"
     }
+  },
+  "cryptoTailMonitor": {
+    "title": "尾盤策略監控",
+    "selectStrategy": "選擇策略",
+    "selectStrategyPlaceholder": "請選擇要監控的策略",
+    "direction": "監控方向",
+    "directionUp": "Up",
+    "directionDown": "Down",
+    "noData": "請選擇一個策略開始監控",
+    "priceRange": "價格區間",
+    "timeWindow": "時間窗口",
+    "stat": {
+      "openPrice": "開盤價",
+      "currentPrice": "最新價",
+      "spread": "價差",
+      "remainingTime": "剩餘時間",
+      "configuredSpread": "配置價差",
+      "configuredSpreadMin": "最小價差",
+      "configuredSpreadMax": "最大價差",
+      "status": "狀態",
+      "minSpreadLine": "最小價差線",
+      "periodSpreadMinMax": "週期內價差",
+      "periodSpreadMin": "週期內最小價差",
+      "periodSpreadMax": "週期內最大價差",
+      "minSpread": "最小",
+      "maxSpread": "最大"
+    },
+    "status": {
+      "triggered": "已觸發",
+      "periodEnded": "週期結束",
+      "inCondition": "滿足條件",
+      "waiting": "等待中"
+    },
+    "chart": {
+      "title": "分時圖",
+      "btcTitle": "BTC 分時圖",
+      "marketTitle": "市場分時圖",
+      "price": "BTC 價格",
+      "openPrice": "開盤價",
+      "spread": "價差",
+      "minSpreadLine": "最小價差線",
+      "marketUp": "Up",
+      "marketDown": "Down",
+      "time": "時間"
+    },
+    "strategyInfo": {
+      "title": "策略信息",
+      "market": "市場",
+      "interval": "週期",
+      "account": "賬戶",
+      "spreadMode": "價差模式"
+    }
   }
 }