feat: 实现回测功能

## 功能概述
实现完整的回测功能，支持基于历史数据模拟跟单策略的执行效果。

## 后端实现
- 数据库：新增 backtest_task 和 backtest_trade 表（V27迁移脚本）
- 实体类：BacktestTask、BacktestTrade
- Repository：BacktestTaskRepository、BacktestTradeRepository
- Service：
  - BacktestService：回测任务管理（CRUD）
  - BacktestDataService：从 Polymarket Data API 获取历史交易数据
  - BacktestExecutionService：回测算法核心实现
  - BacktestPollingService：定时轮询执行回测任务
- Controller：BacktestController（6个API接口）
- DTO：BacktestDto、TradeData
- 错误码：新增回测相关错误码和国际化消息

## 前端实现
- 页面组件：
  - BacktestList：回测任务列表
  - BacktestCreate：创建回测任务
  - BacktestDetail：回测详情（含图表）
  - BacktestChart：资金曲线图表（使用 ECharts）
- 类型定义：backtest.ts
- API 服务：集成所有回测接口
- 国际化：支持中英文

## 核心特性
- 回测天数限制：1-15 天
- 数据获取：直接从 Polymarket Data API 获取历史交易（不使用缓存表）
- 任务执行：同一时刻只执行一个任务，按创建时间顺序执行最早创建的任务
- 回测算法：完整实现市场结算、卖出匹配、价格容忍度、每日订单限制等规则
- 实时进度：支持任务进度更新和实时轮询

## 文档更新
- BACKTEST_PRD.md：产品需求文档
- BACKTEST_TECHNICAL_DESIGN.md：技术设计文档
- BACKTEST_REVIEW_CHECKLIST.md：设计评审检查清单

## 其他修改
- 移除 max_position_count 配置（V26迁移脚本）
- 移除 BacktestSyncService（不再需要实时同步）
- 修复前后端编译错误

frontend/src/locales/en/common.json

@@ -240,6 +240,7 @@
     "templates": "Templates",
     "copyTradingConfig": "Copy Trading Config",
     "positions": "Position Management",
+    "backtest": "Backtest",
     "statistics": "Statistics",
     "announcements": "Announcements",
     "users": "User Management",
@@ -1226,5 +1227,105 @@
     "providerQuickNode": "QuickNode",
     "providerChainstack": "Chainstack",
     "providerGetBlock": "GetBlock"
+  },
+  "backtest": {
+    "title": "Backtest",
+    "taskName": "Task Name",
+    "leader": "Leader",
+    "initialBalance": "Initial Balance",
+    "backtestDays": "Backtest Days",
+    "status": "Status",
+    "progress": "Progress",
+    "startTime": "Start Time",
+    "endTime": "End Time",
+    "finalBalance": "Final Balance",
+    "profitAmount": "Profit Amount",
+    "profitRate": "Profit Rate",
+    "totalTrades": "Total Trades",
+    "buyTrades": "Buy Trades",
+    "sellTrades": "Sell Trades",
+    "winTrades": "Win Trades",
+    "lossTrades": "Loss Trades",
+    "winRate": "Win Rate",
+    "maxProfit": "Max Profit",
+    "maxLoss": "Max Loss",
+    "maxDrawdown": "Max Drawdown",
+    "avgHoldingTime": "Avg Holding Time",
+    "statusPending": "Pending",
+    "statusRunning": "Running",
+    "statusCompleted": "Completed",
+    "statusStopped": "Stopped",
+    "statusFailed": "Failed",
+    "createTask": "Create Backtest Task",
+    "taskList": "Backtest Task List",
+    "taskDetail": "Backtest Task Detail",
+    "tradeRecords": "Trade Records",
+    "config": "Configuration",
+    "statistics": "Statistics",
+    "chart": "Balance Chart",
+    "createSuccess": "Created successfully",
+    "createFailed": "Failed to create",
+    "deleteSuccess": "Deleted successfully",
+    "deleteFailed": "Failed to delete",
+    "stopSuccess": "Stopped successfully",
+    "stopFailed": "Failed to stop",
+    "deleteConfirm": "Are you sure you want to delete this backtest task?",
+    "stopConfirm": "Are you sure you want to stop this backtest task?",
+    "noTasks": "No backtest tasks",
+    "noTrades": "No trade records",
+    "fetchTasksFailed": "Failed to fetch task list",
+    "fetchTaskDetailFailed": "Failed to fetch task detail",
+    "fetchTradesFailed": "Failed to fetch trade records",
+    "balanceChart": "Balance Change",
+    "pnlChart": "PnL Change",
+    "executionTime": "Execution Time",
+    "runningDuration": "Running Duration",
+    "estimatedRemaining": "Estimated Remaining",
+    "leaderAddress": "Leader Address",
+    "leaderName": "Leader Name",
+    "copyMode": "Copy Mode",
+    "copyModeRatio": "Ratio",
+    "copyModeFixed": "Fixed Amount",
+    "copyRatio": "Copy Ratio",
+    "fixedAmount": "Fixed Amount",
+    "maxOrderSize": "Max Order Size",
+    "minOrderSize": "Min Order Size",
+    "maxDailyLoss": "Max Daily Loss",
+    "maxDailyOrders": "Max Daily Orders",
+    "priceTolerance": "Price Tolerance",
+    "delaySeconds": "Delay Seconds",
+    "supportSell": "Support Sell",
+    "minOrderDepth": "Min Order Depth",
+    "maxSpread": "Max Spread",
+    "minPrice": "Min Price",
+    "maxPrice": "Max Price",
+    "maxPositionValue": "Max Position Value",
+    "keywordFilterMode": "Keyword Filter Mode",
+    "keywordFilterModeDisabled": "Disabled",
+    "keywordFilterModeWhitelist": "Whitelist",
+    "keywordFilterModeBlacklist": "Blacklist",
+    "keywords": "Keywords",
+    "maxMarketEndDate": "Market End Date Limit",
+    "tradeTime": "Trade Time",
+    "marketId": "Market ID",
+    "marketTitle": "Market Title",
+    "side": "Side",
+    "sideBuy": "Buy",
+    "sideSell": "Sell",
+    "sideSettlement": "Settlement",
+    "outcome": "Outcome",
+    "quantity": "Quantity",
+    "price": "Price",
+    "amount": "Amount",
+    "fee": "Fee",
+    "profitLoss": "Profit/Loss",
+    "balanceAfter": "Balance After",
+    "leaderTradeId": "Leader Trade ID",
+    "loading": "Loading...",
+    "refreshing": "Refreshing...",
+    "starting": "Starting...",
+    "stopping": "Stopping...",
+    "errorOccurred": "Error occurred",
+    "retry": "Retry"
   }
 }