feat: Add dynamic OG images and Schema.org structured data

- Add satori + resvg for programmatic OG image generation (1200x630)
- Create 42 per-page OG images with LUMOS branding (dark gradient style)
- Override Starlight Head component with og:image, twitter:image
- Add Schema.org JSON-LD (Organization, WebSite, SoftwareApplication, WebPage)
- Add build:og script for manual regeneration

Closes #102

Author: rz1989s

astro.config.mjs

@@ -14,6 +14,7 @@ export default defineConfig({
 				src: './src/assets/logo.png',
 			},
 			components: {
+				Head: './src/components/Head.astro',
 				Footer: './src/components/Footer.astro',
 			},
 			social: [