레이아웃: 헤더 + 사이드바 + 메인 + 푸터

RootLayout (전체)
├── (marketing)/layout — 헤더 + 푸터 (랜딩)
├── (auth)/layout — 헤더 only (로그인)
└── (app)/layout — 헤더 + 사이드바 + 푸터 (인증 필요)

// src/app/(app)/layout.tsx
import { redirect } from 'next/navigation'
import { createClient } from '@/lib/supabase/server'
import { Sidebar } from '@/components/app/sidebar'
import { Header } from '@/components/app/header'

export default async function AppLayout({ children }: { children: React.ReactNode }) {
  const supabase = await createClient()
  const { data: { user } } = await supabase.auth.getUser()

  if (!user) redirect('/login')

  return (
    <div className="flex h-screen">
      <Sidebar />
      <div className="flex-1 flex flex-col overflow-hidden">
        <Header user={user} />
        <main className="flex-1 overflow-y-auto p-6">{children}</main>
      </div>
    </div>
  )
}

// src/components/app/header.tsx
'use client'
import { Bell, Search } from 'lucide-react'
import { UserMenu } from './user-menu'
import { ThemeToggle } from '@/components/theme-toggle'

export function Header({ user }: { user: User }) {
  return (
    <header className="border-b bg-background h-14 flex items-center px-6 gap-4">
      <div className="flex-1 max-w-md relative">
        <Search className="absolute left-3 top-1/2 -translate-y-1/2 h-4 w-4 text-muted-foreground" />
        <input
          placeholder="검색..."
          className="w-full pl-9 pr-3 py-1.5 bg-muted rounded-md text-sm"
        />
      </div>
      <button className="relative">
        <Bell className="h-5 w-5" />
        <span className="absolute -top-1 -right-1 h-2 w-2 bg-red-500 rounded-full" />
      </button>
      <ThemeToggle />
      <UserMenu user={user} />
    </header>
  )
}

// src/components/app/sidebar.tsx
'use client'
import Link from 'next/link'
import { usePathname } from 'next/navigation'
import { Home, Sparkles, History, Settings } from 'lucide-react'
import { cn } from '@/lib/utils'

const NAV = [
  { href: '/dashboard', label: '대시보드', icon: Home },
  { href: '/generate', label: 'AI 생성', icon: Sparkles },
  { href: '/history', label: '히스토리', icon: History },
  { href: '/settings', label: '설정', icon: Settings },
]

export function Sidebar() {
  const pathname = usePathname()
  return (
    <aside className="hidden md:flex w-60 border-r bg-muted/30 flex-col">
      <div className="p-6">
        <Link href="/dashboard" className="font-bold text-lg">My SaaS</Link>
      </div>
      <nav className="flex-1 px-3 space-y-1">
        {NAV.map(({ href, label, icon: Icon }) => (
          <Link
            key={href}
            href={href}
            className={cn(
              'flex items-center gap-3 px-3 py-2 rounded-md text-sm',
              pathname === href
                ? 'bg-primary text-primary-foreground'
                : 'hover:bg-muted'
            )}
          >
            <Icon className="h-4 w-4" />
            {label}
          </Link>
        ))}
      </nav>
    </aside>
  )
}

// src/components/app/mobile-sidebar.tsx
'use client'
import { Sheet, SheetContent, SheetTrigger } from '@/components/ui/sheet'
import { Menu } from 'lucide-react'
import { Sidebar } from './sidebar'

export function MobileSidebar() {
  return (
    <Sheet>
      <SheetTrigger className="md:hidden">
        <Menu />
      </SheetTrigger>
      <SheetContent side="left" className="p-0 w-60">
        <Sidebar />
      </SheetContent>
    </Sheet>
  )
}