feat: Add dynamic Open Graph image generation with correct aspect ratio

- Create /api/og-image endpoint that generates SVG with 1.91:1 ratio (1200x630px)
- Prevents logo cropping on Facebook and Twitter
- Uses safe padding (150px) to ensure content is never cut off
- Update default OG image to use dynamic endpoint
- Add SEO testing documentation

lib/config.ts

@@ -14,7 +14,7 @@ export const config = {
         linkUrl: process.env.NEXT_PUBLIC_CREDITS_LINK_URL || 'https://digitalcourage.social/@elpatron',
     },
     seo: {
-        ogImage: process.env.NEXT_PUBLIC_OG_IMAGE || '/favicon.ico',
+        ogImage: process.env.NEXT_PUBLIC_OG_IMAGE || '/api/og-image',
         twitterHandle: process.env.NEXT_PUBLIC_TWITTER_HANDLE || undefined,
     }
 };