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/Header.tsx

@@ -0,0 +1,44 @@
+import { LogoutOutlined, UserOutlined } from '@ant-design/icons'
+import { Dropdown, Layout, Space, Typography } from 'antd'
+import { useNavigate } from 'react-router-dom'
+import { useTranslation } from 'react-i18next'
+
+import apiClient from '../../api/client'
+import { useAuthStore } from '../../stores/auth'
+
+const { Header: AntHeader } = Layout
+
+export default function Header() {
+  const { t } = useTranslation()
+  const navigate = useNavigate()
+  const user = useAuthStore((s) => s.user)
+  const clear = useAuthStore((s) => s.clear)
+
+  const onLogout = async () => {
+    try { await apiClient.post('/auth/logout') } catch { /* ignore */ }
+    clear()
+    navigate('/login', { replace: true })
+  }
+
+  return (
+    <AntHeader style={{ background: '#fff', padding: '0 24px', display: 'flex', justifyContent: 'flex-end' }}>
+      <Dropdown
+        menu={{
+          items: [
+            {
+              key: 'logout',
+              icon: <LogoutOutlined />,
+              label: t('auth.logout'),
+              onClick: onLogout,
+            },
+          ],
+        }}
+      >
+        <Space style={{ cursor: 'pointer' }}>
+          <UserOutlined />
+          <Typography.Text>{user?.actor ?? '—'}</Typography.Text>
+        </Space>
+      </Dropdown>
+    </AntHeader>
+  )
+}