feat: improve SEO with favicons, optimized OG image, and enhanced schema (#99)

* feat: improve SEO with favicons, optimized OG image, and enhanced schema

- Add favicon PNG assets (16x16, 32x32, 96x96) for better browser/Search display
- Add apple-touch-icon (180x180) for iOS devices
- Add PWA icons (192x192, 512x512) with maskable support
- Optimize OG image from 6.8MB to 279KB (1200x630px)
- Update web manifest with correct icons and theme color (#3CB371)
- Enhance JSON-LD with Organization and WebSite schemas
- Remove hardcoded version from SoftwareApplication schema
- Update sitemap lastmod to 2026-01-29 and changefreq to monthly

* fix: add back softwareVersion for CI sync

* feat: regenerate favicons with high-res transparent image

* feat: replace vocalinux.svg with vocalinux.png in web

web/src/components/icons.tsx

@@ -7,7 +7,7 @@ import Image from "next/image";
 export const VocalinuxLogo: React.FC<{ className?: string }> = ({ className = "" }) => {
   return (
     <Image
-      src="/vocalinux.svg"
+      src="/vocalinux.png"
       alt="Vocalinux Logo"
       width={36}
       height={36}