fix: 优化回测功能UI和修复问题

## 主要修改

### UI 优化
- 将回测功能移到跟单交易菜单下作为子菜单
- 创建回测改为使用 Modal 方式（移除独立页面）
- 优化导航路径，使用 useNavigate 替代 window.location.href

### 功能修复
- 修复 API 路径问题：移除重复的 /api 前缀（/api/backtest -> /backtest）
- 修复 copyRatio 输入框单位：改为百分比输入（100 表示 100%），与跟单配置保持一致
- 修复回测列表中 leader 列显示为空的问题：优先显示 leaderName，为空时显示 leaderAddress

### 多语言完善
- 补充缺失的多语言 key：
  - common.ascending / common.descending / common.day
  - backtest.sortBy / backtest.sortOrder / backtest.createdAt
  - backtest.copyRatioTooltip / backtest.copyRatioPlaceholder
  - 以及其他表单验证相关的 key
- 为中文简体、中文繁体、英文三种语言都添加了完整的翻译

## 修改的文件
- frontend/src/App.tsx - 移除 BacktestCreate 路由
- frontend/src/components/Layout.tsx - 调整菜单结构
- frontend/src/pages/BacktestList.tsx - Modal 创建、修复 leader 显示
- frontend/src/pages/BacktestDetail.tsx - 优化导航
- frontend/src/pages/BacktestCreate.tsx - 同步 copyRatio 修改
- frontend/src/services/api.ts - 修复 API 路径
- frontend/src/locales/* - 补充多语言配置

frontend/src/locales/en/common.json

@@ -34,7 +34,10 @@
     "previous": "Previous",
     "next": "Next",
     "page": "Page",
-    "pageOf": "Page"
+    "pageOf": "Page",
+    "ascending": "Ascending",
+    "descending": "Descending",
+    "day": "day"
   },
   "account": {
     "title": "Account Management",
@@ -1326,6 +1329,25 @@
     "starting": "Starting...",
     "stopping": "Stopping...",
     "errorOccurred": "Error occurred",
-    "retry": "Retry"
+    "retry": "Retry",
+    "taskNameRequired": "Please enter task name",
+    "leaderRequired": "Please select Leader",
+    "initialBalanceRequired": "Please enter initial balance",
+    "initialBalanceInvalid": "Initial balance must be greater than 0",
+    "backtestDaysRequired": "Please enter backtest days",
+    "backtestDaysInvalid": "Backtest days must be between 1-15",
+    "copyRatioRequired": "Please enter copy ratio",
+    "copyRatioInvalid": "Copy ratio must be between 0.01-10000",
+    "copyRatioPlaceholder": "For example: 100 means 100% (1:1 copy), default 100%",
+    "copyRatioTooltip": "Copy ratio represents the percentage of copy amount relative to Leader order amount. For example: 100% means 1:1 copy, 50% means half position copy, 200% means double copy",
+    "fixedAmountRequired": "Please enter fixed amount",
+    "fixedAmountInvalid": "Fixed amount must be greater than 0",
+    "advancedFilters": "Advanced Filters",
+    "keywordsPlaceholder": "Please enter keywords, press Enter to add",
+    "delaySecondsHint": "Delay execution to simulate real copy trading delay",
+    "supportSellHint": "Whether to follow Leader's sell operations",
+    "sortBy": "Sort By",
+    "sortOrder": "Sort Order",
+    "createdAt": "Created At"
   }
 }