chore: .gitignore에 node_modules와 .next 추가 및 제거

Author: leebeanbin

.gitignore

@@ -62,3 +62,22 @@ dmypy.json
 # Ruff
 .ruff_cache/
 .claude/settings.local.json
+
+# Node.js / Frontend
+node_modules/
+.next/
+.nuxt/
+dist/
+build/
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+lerna-debug.log*
+.pnpm-store/
+
+# Frontend build artifacts
+playground/frontend/.next/
+playground/frontend/node_modules/
+playground/frontend/.pnpm-store/