Add full SEO optimization for Spanglish social and language events

- Add comprehensive metadata to root layout with Open Graph, Twitter cards
- Create dynamic sitemap.ts for all pages and events
- Create robots.ts with proper allow/disallow rules
- Add JSON-LD Event structured data to event detail pages
- Add page-specific metadata to events, community, contact, FAQ pages
- Add FAQ structured data schema
- Update footer with local SEO text for Asunción, Paraguay
- Add web manifest for mobile SEO
- Create 404 page with proper noindex
- Optimize image alt text and add lazy loading
- Add NEXT_PUBLIC_SITE_URL env variable
- Add about/ folder to gitignore

frontend/src/app/(public)/events/page.tsx

@@ -108,8 +108,9 @@ export default function EventsPage() {
                     {event.bannerUrl ? (
                       <img 
                         src={event.bannerUrl} 
-                        alt={event.title}
+                        alt={`${event.title} - Spanglish language exchange event in Asunción`}
                         className="h-40 w-full object-cover"
+                        loading="lazy"
                       />
                     ) : (
                       <div className="h-40 bg-gradient-to-br from-primary-yellow/30 to-secondary-blue/20 flex items-center justify-center">