feat: initialize Next.js v15 starter kit with Korean support

Set up Next.js v15 starter kit with App Router architecture including:
- TailwindCSS v4 with CSS-based config and OKLCH color system
- shadcn/ui components (New York style) with Lucide icons
- next-themes for light/dark/system theme toggle (Korean labels)
- Layout components: navbar, footer, theme-toggle
- Import aliases and TypeScript configuration

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.env.example

@@ -0,0 +1,18 @@
+# Next.js 환경변수 예제 파일
+# 이 파일을 .env.local로 복사한 후 실제 값을 입력하세요
+
+# 애플리케이션 설정
+NEXT_PUBLIC_APP_NAME="Next.js Starter Kit"
+NEXT_PUBLIC_APP_DESCRIPTION="Next.js v15, TypeScript, TailwindCSS v4, shadcn/ui로 구성된 스타터 킷"
+
+# 데이터베이스 (예제)
+# DATABASE_URL="postgresql://username:password@localhost:5432/mydb"
+
+# 인증 (예제)
+# NEXTAUTH_SECRET="your-secret-key"
+# NEXTAUTH_URL="http://localhost:3000"
+
+# API 키 (예제)
+# OPENAI_API_KEY="your-openai-api-key"
+# STRIPE_SECRET_KEY="your-stripe-secret-key"
+# STRIPE_PUBLISHABLE_KEY="your-stripe-publishable-key"