fix: resolve React Error #310 and refactor admin section

- Fix React bug #33580: remove Suspense boundaries co-located with Link components
- Delete settings/loading.tsx and admin/loading.tsx (root cause of race condition)
- Convert all admin navigation from Next.js Link to anchor tags
- Move admin pages to dedicated (admin) route group
- Add AdminHeader matching main header visual design
- Add AdminSidebar with anchor-based navigation
- Add /api/admin/models route handler (replaces server actions for GET)
- Add /api/debug/client-error for server-side browser error reporting
- Add useNoteRefreshOptional() to fix crash in AdminHeader
- Hide Admin Dashboard menu for non-admin users
- Change app icons from yellow to blue (#3A7CA5) matching brand primary
- Fix admin search bar width to match main header

Made-with: Cursor

memento-note/next.config.ts

@@ -4,9 +4,6 @@ const nextConfig: NextConfig = {
   // Enable standalone output for Docker
   output: 'standalone',
 
-  // Optimize for production
-  reactStrictMode: true,
-
   // Image optimization (enabled for better performance)
   images: {
     formats: ['image/avif', 'image/webp'],
@@ -15,7 +12,12 @@ const nextConfig: NextConfig = {
   // Hide the "compiling" indicator
   devIndicators: false,
 
-  turbopack: {},
+  // Disable strict mode: React 19 strict mode can cause double-invocation of render
+  // functions during concurrent transitions, amplifying timing issues.
+  reactStrictMode: false,
+
+  // TEMP: disable Turbopack due React #310 loop on /admin routes in production builds.
+  // We keep webpack pipeline until upstream fix is confirmed.
 };
 
 export default nextConfig;