refactor: standardize admin page shell

frontend/src/components/app/AppPage.tsx

@@ -0,0 +1,25 @@
+import type * as React from 'react'
+
+import { cn } from '@/lib/utils'
+
+type AppPageProps = {
+  children: React.ReactNode
+  className?: string
+  contentClassName?: string
+  maxWidth?: '6xl' | '7xl'
+}
+
+const maxWidthClass: Record<NonNullable<AppPageProps['maxWidth']>, string> = {
+  '6xl': 'max-w-6xl',
+  '7xl': 'max-w-7xl'
+}
+
+export function AppPage({ children, className, contentClassName, maxWidth = '7xl' }: AppPageProps) {
+  return (
+    <main className={cn('min-h-screen bg-background px-4 py-4 text-foreground sm:px-6 lg:py-6', className)}>
+      <div className={cn('mx-auto flex flex-col gap-4', maxWidthClass[maxWidth], contentClassName)}>
+        {children}
+      </div>
+    </main>
+  )
+}