feat: replace Tailwind CDN with local build system

- Add tailwind.config.js with theme color configuration
- Add package.json with build scripts and dependencies
- Add Dockerfile Node.js setup for CSS building
- Add input.css for Tailwind processing
- Update all templates to use local CSS and JS instead of CDN
- Add static file serving in main.go
- Download htmx during build process
- Enable CSS minification for production builds

cmd/server/static/input.css

@@ -0,0 +1,5 @@
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+/* Custom theme variables are handled in CSS custom properties in templates */