feat(web): acrylic theme, node flags and icons, build info

Acrylic cards and topbar over a blurred background, country flags, ISP and
OS icons, per-node version tags, a build info footer and an admin versions
tab. Overview cards drop the sparkline and widen the hover area.

web/admin/vite.config.ts

@@ -1,6 +1,7 @@
 import react from '@vitejs/plugin-react'
 import { fileURLToPath } from 'node:url'
 import { defineConfig, loadEnv } from 'vite'
+import { buildDefines } from '../build-info.mjs'
 
 // 开发时把 /api 转发给后端，地址取自环境变量 BACKEND_URL，或 web/.env.local 里的 BACKEND_URL=（见 web/.env.example）：
 //   BACKEND_URL=https://mo.oeo.one npm run dev:display
@@ -9,6 +10,7 @@ export default defineConfig(({ mode }) => {
   const backend = (process.env.BACKEND_URL ?? env.BACKEND_URL ?? 'http://localhost:29181').replace(/\/+$/, '')
   return {
     base: '/admin/',
+    define: buildDefines(mode === 'development'),
     plugins: [react()],
     resolve: { alias: { '@shared': fileURLToPath(new URL('../shared', import.meta.url)) } },
     server: {