feat: enhance header component with complete navigation structure

- Add responsive header with mobile hamburger menu
- Implement user authentication state handling
- Style with primary color scheme using neutral/primary variants
- Add proper navigation links for events and concerts sections
- Include user dropdown menu with profile and logout options

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

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

app/assets/stylesheets/application.postcss.css

@@ -3,7 +3,17 @@
 /* Import Tailwind using PostCSS */
 @import "tailwindcss";
 
+/* Import our custom theme */
+@import "theme";
 
+/* Import components */
+@import "components/hero";
+@import "components/flash";
+@import "components/footer";
+@import "components/event-finder";
+
+/* Import pages */
+@import "pages/home";
 
 /* Base styles */
 body {