refactor: frontend TS migration + Tailwind4/daisyUI5 unify + BUILDPLATFORM docker build

- migrate frontend to TypeScript (vue-tsc strict in build), upgrade all deps to latest (Vite 8, Tailwind 4, daisyUI 5, Pinia 4, vue-router 5)
- restructure frontend dirs (api/components/common/layouts/styles/types/views)
- drop Element Plus, add daisyUI TagInput; main CSS 490KB->163KB, entry JS 618KB->1.3KB
- rewrite Dockerfile(.cn): frontend/backend stages pinned to $BUILDPLATFORM, CGO_ENABLED=0 cross-compile, no QEMU in multi-arch builds; add .dockerignore
- local dev: Vite /api proxy + make dev targets; go:embed all:dist with .gitkeep so backend runs without prior frontend build
- fix latent bugs: Keys.vue users ref, Settings.vue undefined userStore, Login.vue Ref-as-error display, res.error misuse
- add REFACTOR_PLAN.md (phased refactor log)

frontend/src/router/index.ts

@@ -0,0 +1,18 @@
+import { createRouter, createWebHistory } from 'vue-router'
+import { routes } from '@/utils/router_menu'
+
+const router = createRouter({
+  history: createWebHistory(),
+  routes,
+})
+
+router.beforeEach((to, from, next) => {
+  const isAuthenticated = localStorage.getItem('token')
+  if (to.meta.requiresAuth && !isAuthenticated) {
+    next('/login')
+  } else {
+    next()
+  }
+})
+
+export default router