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>

components/layout/ThemeToggle.tsx

@@ -7,6 +7,13 @@ import { Button } from '@/components/ui/Button';
 export function ThemeToggle() {
   const [theme, setTheme] = React.useState<'light' | 'dark'>('light');
 
+  const toggleTheme = React.useCallback(() => {
+    const newTheme = theme === 'light' ? 'dark' : 'light';
+    setTheme(newTheme);
+    localStorage.setItem('theme', newTheme);
+    document.documentElement.classList.toggle('dark', newTheme === 'dark');
+  }, [theme]);
+
   React.useEffect(() => {
     // Check for saved theme preference or default to light
     const savedTheme = localStorage.getItem('theme') as 'light' | 'dark' | null;
@@ -17,12 +24,18 @@ export function ThemeToggle() {
     document.documentElement.classList.toggle('dark', initialTheme === 'dark');
   }, []);
 
-  const toggleTheme = () => {
-    const newTheme = theme === 'light' ? 'dark' : 'light';
-    setTheme(newTheme);
-    localStorage.setItem('theme', newTheme);
-    document.documentElement.classList.toggle('dark', newTheme === 'dark');
-  };
+  // Keyboard shortcut: Ctrl/Cmd + D
+  React.useEffect(() => {
+    const handleKeyDown = (e: KeyboardEvent) => {
+      if (e.key === 'd' && (e.ctrlKey || e.metaKey)) {
+        e.preventDefault();
+        toggleTheme();
+      }
+    };
+
+    window.addEventListener('keydown', handleKeyDown);
+    return () => window.removeEventListener('keydown', handleKeyDown);
+  }, [toggleTheme]);
 
   return (
     <Button