feat(web): add zone-based website management

以稳定 Zone ID 替换旧托管域名详情页：列表展示根域与域名计数，详情提供
概览/域名/路由/证书/设置 Tabs，并补齐 ZoneService 与 vitest 行为测试。
Zone 列表 API 返回 domain_count；同步 Swagger 与重构计划进度。

frontend/app/(main)/websites/[zoneId]/components/zone-route-summary.tsx

@@ -0,0 +1,9 @@
+import {EmptyStateWithBorder} from '@/components/layout/empty'
+import {Card, CardContent, CardDescription, CardHeader, CardTitle} from '@/components/ui/card'
+import type {ZoneDomainItem} from '@/lib/services/openflare'
+import {Route} from 'lucide-react'
+
+export function ZoneRouteSummary({domains}: {domains: ZoneDomainItem[]}) {
+  const groups = Map.groupBy(domains.filter((domain) => domain.proxy_route_id !== null), (domain) => domain.proxy_route_id!)
+  return <Card className="shadow-none"><CardHeader><CardTitle className="text-base">路由关联</CardTitle><CardDescription>域名只能关联一个反代路由；路由可关联多个 Zone 域名。</CardDescription></CardHeader><CardContent>{groups.size === 0 ? <EmptyStateWithBorder icon={Route} description="暂无关联反代路由。" /> : <div className="space-y-3">{[...groups].map(([routeID, items]) => <div key={routeID} className="rounded-lg border p-3"><p className="text-sm font-semibold">路由 #{routeID}</p><p className="mt-1 text-xs text-muted-foreground">{items.map((item) => item.domain).join(' · ')}</p></div>)}</div>}</CardContent></Card>
+}