feat: add favicon (Images by Olofsson logo) (#26)

Render logo to square PNG favicons (32/180/512px) and link them in
MainLayout.astro head. Previously the active layout had no favicon.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/layouts/MainLayout.astro

@@ -6,6 +6,9 @@ const { title } = Astro.props;
 <html lang="sv" class="scroll-smooth"> <head>
     <meta charset="utf-8" />
     <meta name="viewport" content="width=device-width" />
+    <link rel="icon" type="image/png" sizes="32x32" href="/favicon-32.png" />
+    <link rel="icon" type="image/png" sizes="512x512" href="/favicon-512.png" />
+    <link rel="apple-touch-icon" sizes="180x180" href="/favicon-180.png" />
     <title>{title}</title>
   </head>
   <body class="bg-neutral-900 text-white font-sans antialiased min-h-screen flex flex-col">