Migrate from Rollup.js to Vite build system

[Copilot]

This PR migrates the build system from Rollup.js to Vite for improved development experience and build performance.

Key Changes

Build System Migration

• Replaced Rollup with Vite: Leverages Vite's faster development server with Hot Module Replacement (HMR)
• Created vite.config.js: Equivalent functionality to the previous rollup.config.js with modern configuration
• Updated package.json scripts: Changed from rollup -c to vite commands

Dependency Updates

• Updated all dependencies to latest versions for security and performance improvements
• Removed unused packages: Eliminated Rollup-specific plugins and Babel configuration since Vite handles TypeScript compilation natively with esbuild
• Added Vite plugins:
  • @vitejs/plugin-legacy for legacy browser support
  • vite-plugin-static-copy for asset copying

Configuration Changes

• Moved index.html from src/ to project root (Vite convention)
• Ported custom iife-str plugin to work with Vite for Web Worker support
• Removed .babelrc: No longer needed as Vite handles TypeScript compilation
• Removed rollup.config.js: Replaced by Vite configuration

Docker Updates

• Updated Node.js version from 16 to 18 in Dockerfile for better performance and security

Features Preserved

• ✅ TypeScript compilation (now via esbuild instead of Babel)
• ✅ CSS processing with imports
• ✅ Markdown file processing
• ✅ Asset copying from src/assets/
• ✅ Web Worker support via custom plugin
• ✅ Development server with live reload (now HMR)
• ✅ Production builds with minification
• ✅ Legacy browser support

Performance Improvements

• Faster dev server startup: Vite's native ESM approach vs Rollup bundling
• Hot Module Replacement: Instant updates without full page reloads
• Faster builds: esbuild-based compilation
• Reduced bundle size: Eliminated unnecessary dependencies

Testing

• ✅ All existing tests pass
• ✅ Production build generates identical output structure
• ✅ Development server runs successfully
• ✅ Custom Web Worker functionality preserved

Build times remain similar (~9-10 seconds) while providing enhanced development experience and modern tooling.

Fixes #133.

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