fix: switch logo back to SVG (transparent background)

PNG had dark background baked in, looked bad against Starlight's header.
SVG has transparent bg and works on both light and dark themes.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: NEOxplus

astro.config.mjs

@@ -10,7 +10,7 @@ export default defineConfig({
 			title: 'GEN API',
 			favicon: '/favicon.png',
 			logo: {
-				src: './src/assets/logo.png',
+				src: './src/assets/logo.svg',
 				replacesTitle: true,
 			},
 			head: [