feat(admin): Phase 0 平台超管基础 — is_platform_admin + IsPlatformAdmin + create_platform_admin(admin/admin123) + AdminAuditLog + Admin 后台外壳与路由 gating

后端:User.is_platform_admin + migration;权限类 IsPlatformAdmin;管理命令建 admin/admin123(幂等);
AdminAuditLog 模型 + log_admin_action() helper;me/login 对无团队超管优雅返回 team=null;UserSerializer 暴露标志。
前端:routes/admin 后台外壳(分组侧栏 + 概览 + 占位)、/admin 路由解析与 gating(超管直落、非超管纠回)、
侧栏平台入口、admin-page.css(仅 token)、IconKitSvg 补图标。
测试:accounts 11/11 单测过;无头 e2e _admin-p0.mjs 全断言过 + 0 console error;tsc+build 绿。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

core/frontend/src/routes/route-config.ts

@@ -40,6 +40,8 @@ export type ResolvedRoute = {
   productId?: string;
   projectId?: string;
   hash?: string;
+  // 平台超管后台:/admin → ""(概览),/admin/<section> → section slug。undefined = 非 admin 路由。
+  admin?: string;
 };
 export type NavigateOptions = {
   productId?: string;
@@ -113,6 +115,11 @@ export function resolveRoute(): ResolvedRoute {
 
   if (path === "/register" || hash === "register") return { page: "dashboard", authMode: "register", hash };
   if (path === "/login") return { page: "dashboard", authMode: "login", hash };
+  // 平台超管后台:独立外壳,page 仅占位(渲染由 route.admin 接管)
+  if (path === "/admin") return { page: "dashboard", authMode: "login", admin: "", hash };
+  if (path.startsWith("/admin/")) {
+    return { page: "dashboard", authMode: "login", admin: path.slice("/admin/".length), hash };
+  }
   if (path === "/" && isPage(hash)) return { page: hash, authMode: "login", hash };
   if (path === "/" || path === "/dashboard") return { page: "dashboard", authMode: "login", hash };
   if (path === "/products") return { page: "products", authMode: "login", hash };