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/components/admin-sidebar.tsx

@@ -1,6 +1,5 @@
 'use client'
 
-import Link from 'next/link'
 import { usePathname } from 'next/navigation'
 import { LayoutDashboard, Users, Brain, Settings } from 'lucide-react'
 import { cn } from '@/lib/utils'
@@ -55,7 +54,10 @@ export function AdminSidebar({ className }: AdminSidebarProps) {
           const isActive = pathname === item.href || (item.href !== '/admin' && pathname?.startsWith(item.href))
 
           return (
-            <Link
+            // <a> instead of <Link>: avoids Next.js RSC navigation transitions
+            // that trigger React Error #310 (React bug #33580) in production.
+            // Full-page reloads are acceptable for admin navigation.
+            <a
               key={item.href}
               href={item.href}
               className={cn(
@@ -68,7 +70,7 @@ export function AdminSidebar({ className }: AdminSidebarProps) {
             >
               {item.icon}
               <span>{t(item.titleKey)}</span>
-            </Link>
+            </a>
           )
         })}
       </nav>