feat: add keyboard shortcuts, Docker deployment, and production build

Major improvements for production deployment and UX:

**Keyboard Shortcuts System**
- `/` - Focus font search instantly
- `Esc` - Clear search and close dialogs
- `Ctrl/Cmd + D` - Toggle dark/light mode
- `Shift + ?` - Show keyboard shortcuts help dialog
- Floating keyboard icon button for discoverability
- Beautiful modal with all shortcuts listed
- Global event listeners with proper cleanup

**Enhanced Search UX**
- Updated placeholder: "Search fonts... (Press / to focus)"
- Auto-focus on `/` keypress
- Auto-clear and blur on `Escape`
- Ref-based input focusing for reliability

**Docker Deployment**
- Multi-stage Dockerfile (deps, builder, nginx runner)
- Based on node:22-alpine for minimal size
- Static export served via nginx:alpine
- Built-in health check endpoint (/health)
- Optimized for production

**Nginx Configuration**
- Gzip compression for all text assets
- Aggressive caching for static assets (1 year)
- Security headers (X-Frame-Options, CSP, etc.)
- SPA routing support (try_files)
- Health check endpoint
- Performance tuning (sendfile, tcp_nopush)

**Documentation Updates**
- Corrected font count to accurate 373 fonts
- Updated README and IMPLEMENTATION_PLAN
- Added Docker deployment instructions
- Clarified .flf vs .tlf vs .flc formats

**Production Build**
- Tested static export build
- Total size: 8.0MB (including all fonts!)
- 4.7s build time with Turbopack
- All routes pre-rendered successfully
- Ready for CDN/static hosting

**Technical Highlights**
- useKeyboardShortcuts custom hook
- Event listener cleanup on unmount
- Ref forwarding for input focus
- Modal dialog with backdrop blur
- Keyboard-first navigation

The app is now production-ready with professional keyboard shortcuts
and Docker deployment support! 🎉

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

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

app/page.tsx

@@ -1,5 +1,6 @@
 import { FigletConverter } from '@/components/converter/FigletConverter';
 import { ThemeToggle } from '@/components/layout/ThemeToggle';
+import { KeyboardShortcutsHelp } from '@/components/ui/KeyboardShortcutsHelp';
 
 export default function Home() {
   return (
@@ -41,6 +42,8 @@ export default function Home() {
           </p>
         </footer>
       </div>
+
+      <KeyboardShortcutsHelp />
     </main>
   );
 }