feat(leader): Leader 管理展示跟单/回测数量并支持跳转筛选

- 后端：LeaderDto 增加 backtestCount，LeaderService 统计回测数并返回
- Leader 列表：展示跟单数、回测数，点击跳转跟单配置/回测页并带 leaderId 筛选
- 跟单配置页：从 URL 读取 leaderId 并应用筛选，Leader 下拉改用 LeaderSelect
- 回测页：支持 Leader 筛选，页面加载时请求 Leader 列表，筛选与详情统一显示规则
- LeaderSelect：支持 style，回测/跟单筛选统一使用
- 多语言：补充 leaderList 相关 key
- 移动端：Leader 管理卡片内按钮增加内边距 padding 8px 16px

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

frontend/src/locales/en/common.json

@@ -434,7 +434,10 @@
     "openWebsite": "Open Website",
     "all": "All",
     "copyTradingCount": "Copy Trading Count",
+    "backtestCount": "Backtest Count",
     "copyTradingRelations": "{{count}} copy trading relations",
+    "viewCopyTradings": "View Copy Tradings",
+    "viewBacktests": "View Backtests",
     "createdAt": "Created At",
     "noData": "No Leader data",
     "fetchFailed": "Failed to get Leader list",
@@ -442,7 +445,9 @@
     "deleteFailed": "Failed to delete Leader",
     "deleteConfirm": "Are you sure you want to delete this Leader?",
     "deleteConfirmDesc": "This Leader has {{count}} copy trading relations, please delete them first",
-    "openDetailFailed": "Failed to open detail"
+    "openDetailFailed": "Failed to open detail",
+    "noCopyTradings": "No copy trading configs",
+    "noBacktests": "No backtests"
   },
   "leaderAdd": {
     "title": "Add Leader",