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>

.dockerignore

@@ -0,0 +1,44 @@
+# Dependencies
+node_modules
+npm-debug.log
+yarn-error.log
+pnpm-debug.log
+
+# Next.js
+.next
+out
+
+# Environment variables
+.env
+.env*.local
+
+# Git
+.git
+.gitignore
+
+# IDE
+.vscode
+.idea
+*.swp
+*.swo
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Documentation
+README.md
+PLAN.md
+*.md
+
+# Docker
+Dockerfile
+docker-compose.yml
+.dockerignore
+
+# Testing
+coverage
+.nyc_output
+
+# Misc
+*.log