Add logo image and update branding across header, footer, and emails

- Replace text logo with logo-spanglish.png in Header and Footer
- Update email templates to use logo image instead of styled text
- Add new HeroSection and EventHighlight components
- Update homepage layout and event detail pages
- Adjust Tailwind config and global styles

frontend/tailwind.config.js

@@ -10,7 +10,7 @@ module.exports = {
       colors: {
         // Brand colors from brand.md
         primary: {
-          yellow: '#FFD84D',
+          yellow: '#FBB82B',
           dark: '#111111',
           white: '#FFFFFF',
         },
@@ -20,10 +20,13 @@ module.exports = {
           blue: '#2F80ED',
           brown: '#6B4A2B',
         },
+        brand: {
+          navy: '#002F44',
+        },
       },
       fontFamily: {
-        sans: ['Inter', 'system-ui', 'sans-serif'],
-        heading: ['Poppins', 'Inter', 'system-ui', 'sans-serif'],
+        sans: ['var(--font-inter)', 'system-ui', 'sans-serif'],
+        heading: ['var(--font-poppins)', 'var(--font-inter)', 'system-ui', 'sans-serif'],
       },
       borderRadius: {
         'btn': '12px',