feat: 在创建跟单配置时显示Leader资产信息

- 选择Leader后自动获取并显示资产信息（总资产、可用余额、仓位资产）
- 在AddModal和EditModal中都实现该功能
- 使用Card和Statistic组件美观展示
- 添加中英文多语言支持
- 使用formatUSDC格式化显示金额

frontend/src/locales/en/common.json

@@ -840,7 +840,13 @@
     "noAccounts": "No accounts",
     "importAccount": "Import Account",
     "noLeaders": "No Leaders",
-    "addLeader": "Add Leader"
+    "addLeader": "Add Leader",
+    "leaderAssetInfo": "Leader Asset Info",
+    "loadingAssetInfo": "Loading asset info...",
+    "totalAsset": "Total Assets",
+    "availableBalance": "Available Balance",
+    "positionAsset": "Position Assets",
+    "fetchAssetInfoFailed": "Failed to fetch asset info"
   },
   "copyTradingEdit": {
     "title": "Edit Copy Trading Config",

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

@@ -840,7 +840,13 @@
     "noAccounts": "暂无账户",
     "importAccount": "导入账户",
     "noLeaders": "暂无 Leader",
-    "addLeader": "添加 Leader"
+    "addLeader": "添加 Leader",
+    "leaderAssetInfo": "Leader 资产信息",
+    "loadingAssetInfo": "加载资产信息中...",
+    "totalAsset": "总资产",
+    "availableBalance": "可用余额",
+    "positionAsset": "仓位资产",
+    "fetchAssetInfoFailed": "获取资产信息失败"
   },
   "copyTradingEdit": {
     "title": "编辑跟单配置",

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

@@ -837,10 +837,16 @@
     "fetchLeaderFailed": "獲取 Leader 列表失敗",
     "fetchTemplateFailed": "獲取模板列表失敗",
     "templateName": "模板名稱",
-    "noAccounts": "暫無賬戶",
-    "importAccount": "導入賬戶",
+    "noAccounts": "暫無帳戶",
+    "importAccount": "導入帳戶",
     "noLeaders": "暫無 Leader",
-    "addLeader": "添加 Leader"
+    "addLeader": "添加 Leader",
+    "leaderAssetInfo": "Leader 資產資訊",
+    "loadingAssetInfo": "加載資產資訊中...",
+    "totalAsset": "總資產",
+    "availableBalance": "可用餘額",
+    "positionAsset": "倉位資產",
+    "fetchAssetInfoFailed": "獲取資產資訊失敗"
   },
   "copyTradingEdit": {
     "title": "編輯跟單配置",