feat(frontend): 尾盘父级菜单与图标优化

- 尾盘策略、尾盘监控归入「尾盘」父级菜单，与跟单交易结构一致
- 菜单图标：父级 LineChart，尾盘策略 RocketOutlined，尾盘监控 DashboardOutlined
- 多语言：新增 menu.cryptoTail（尾盘/尾盤/Crypto Tail）
- 含 CryptoTailMonitor 及后端 DTO/Service 等修改

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

frontend/src/locales/en/common.json

@@ -312,6 +312,7 @@
     "leaders": "Leader Management",
     "templates": "Templates",
     "copyTradingConfig": "Copy Trading Config",
+    "cryptoTail": "Crypto Tail",
     "cryptoTailStrategy": "Tail Strategy",
     "cryptoTailMonitor": "Tail Monitor",
     "positions": "Position Management",