feat(ui): Frontend MVP — React 19 + AntD 6 + Vite + StaticFS-Wiring

Scaffold und Core-Infrastruktur 1:1 nach enconf-Pattern (netcell-
webpanel/management-ui), reduziert auf EdgeGuard-Scope (kein reseller/
customer-Roles, keine codemirror/extensions). Stack: React 19 + AntD 6
+ TS strict + Vite + TanStack-Query + zustand + react-i18next.

Layout: AppLayout (Sider+Header+Content), Sidebar (Dashboard/Domains),
Header (User-Dropdown + Logout). i18n mit de/en common.json.

Pages: Login (POST /auth/login), Setup-Wizard (POST /setup/complete),
Dashboard (Health-Polling + Statistics), Domains (volles CRUD via
TanStack-Query gegen /domains-API). UpdateBanner-Komponente
(/system/package-versions, alle 5 min poll, /system/upgrade trigger)
ist von Tag 1 wie vom User gefordert eingebaut.

API-Wiring: cmd/edgeguard-api/main.go mountUI() — gin StaticFS für
/usr/share/edgeguard/ui/ (overridebar via EDGEGUARD_UI_DIR), echte
Files werden direkt geserved, alle nicht-API-Pfade fallen via
NoRoute auf index.html für React-Router-SPA. Wenn dist/ fehlt:
HTML-Placeholder mit Build-Hinweis.

Verifiziert: bun install + npx tsc -b strict (0 errors) + bun run
build (12 chunks). End-to-end gegen /tmp/eg-api: / serviert echte
React-index.html, /domains SPA-Fallback, /api/v1/* JSON, /assets/*
direkt, /api/v1/nonexistent korrekt 404.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

management-ui/src/components/Layout/Sidebar.tsx

@@ -0,0 +1,30 @@
+import { DashboardOutlined, GlobalOutlined } from '@ant-design/icons'
+import { Menu, Typography } from 'antd'
+import { useNavigate, useLocation } from 'react-router-dom'
+import { useTranslation } from 'react-i18next'
+
+export default function Sidebar() {
+  const { t } = useTranslation()
+  const navigate = useNavigate()
+  const location = useLocation()
+
+  const items = [
+    { key: '/dashboard', icon: <DashboardOutlined />, label: t('nav.dashboard') },
+    { key: '/domains', icon: <GlobalOutlined />, label: t('nav.domains') },
+  ]
+
+  return (
+    <div>
+      <Typography.Title level={4} style={{ color: '#fff', padding: '16px', margin: 0 }}>
+        {t('app.title')}
+      </Typography.Title>
+      <Menu
+        theme="dark"
+        mode="inline"
+        selectedKeys={[location.pathname]}
+        items={items}
+        onClick={(e) => navigate(e.key)}
+      />
+    </div>
+  )
+}