refactor(frontend): API 子模块化、大组件拆分与 TanStack Query hooks

P1: kubernetes/system API 拆为子目录模块，导出工具下沉到 lib/export-utils，
    http 统一 buildApiUrl/getWsBase；HostMonitor、DeploymentEdit* 拆至子组件。

P2: 新增 hooks/api（queryKeys、useTerminalSessions、useHostMonitor），
    TerminalSessionsTab 与 HostMonitor 接入 TanStack Query。

P3: 保留 services/api 路径，未迁移至 api/ 目录。

backend/static/assets/dashboard-BHNKEvkq.js

@@ -0,0 +1 @@
+import{h as t}from"./index-Dmami9WE.js";const a={getStats:async()=>t.get("/dashboard/stats"),getAlerts:async e=>t.get("/dashboard/recent-alerts",e?{limit:e}:void 0),getReleases:async e=>t.get("/dashboard/recent-releases",e?{limit:e}:void 0),getMetrics:async e=>t.get("/dashboard/metrics",e?{hours:e}:void 0)};export{a as d};