feat: initialize Next.js 16 project with Tailwind CSS 4 and Docker support

Phase 1 Implementation:
- Set up Next.js 16 with React 19, TypeScript 5, and Turbopack
- Configure Tailwind CSS 4 with OKLCH color system
- Implement dark/light theme support
- Create core UI components: Button, Card, Slider, Progress, Toast
- Add ThemeToggle component for theme switching
- Set up project directory structure for audio editor
- Create storage utilities for settings management
- Add Dockerfile with multi-stage build (Node + nginx)
- Configure nginx for static file serving with caching
- Add docker-compose.yml for easy deployment
- Configure static export mode for production

Tech Stack:
- Next.js 16 with Turbopack
- React 19
- TypeScript 5
- Tailwind CSS 4
- pnpm 9.0.0
- nginx 1.27 (for Docker deployment)

Build verified and working ✓

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.gitignore

@@ -0,0 +1,53 @@
+# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
+
+# dependencies
+/node_modules
+/.pnp
+.pnp.*
+.yarn/*
+!.yarn/patches
+!.yarn/plugins
+!.yarn/releases
+!.yarn/versions
+
+# testing
+/coverage
+
+# next.js
+/.next/
+/out/
+
+# production
+/build
+
+# misc
+.DS_Store
+*.pem
+
+# debug
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+.pnpm-debug.log*
+
+# local env files
+.env*.local
+.env
+
+# vercel
+.vercel
+
+# typescript
+*.tsbuildinfo
+next-env.d.ts
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# OS
+Thumbs.db