feat: add full favicon & PWA meta tags to head

Adds apple-touch-icon, PNG favicons, webmanifest link, and
msapplication-TileColor; existing SVG/ICO fallbacks retained.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

layouts/partials/head.html

@@ -69,6 +69,11 @@
 {{- end -}}
 <link rel="stylesheet" href="{{ $css.RelPermalink }}"{{ if eq hugo.Environment "production" }} integrity="{{ $css.Data.Integrity }}"{{ end }}>
 
-<!-- Favicon -->
+<!-- Favicon & PWA -->
+<link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png">
+<link rel="icon" type="image/png" sizes="32x32" href="/favicon-32x32.png">
+<link rel="icon" type="image/png" sizes="16x16" href="/favicon-16x16.png">
 <link rel="icon" href="/favicon.svg" type="image/svg+xml">
 <link rel="icon" href="/favicon.ico" sizes="any">
+<link rel="manifest" href="/site.webmanifest">
+<meta name="msapplication-TileColor" content="#050510">