feat(docs): replace logo with SVG and update navigation styling

- Replace PNG logo with high-definition SVG version for better quality and scalability
- Update navigation to use logo image instead of text title for improved branding
- Add custom styling for logo display in navigation bar
- Exclude navigation logo from automatic image styling rules
- Update sitemap timestamps to reflect recent changes

docs/public/sitemap.xml

@@ -3,7 +3,7 @@
          xmlns:xhtml="http://www.w3.org/1999/xhtml">
   <url>
     <loc>https://datawhalechina.github.io/easy-vibe/zh-cn/</loc>
-    <lastmod>2026-03-16T00:53:29+08:00</lastmod>
+    <lastmod>2026-03-18T12:12:42+08:00</lastmod>
     <changefreq>weekly</changefreq>
     <priority>1.0</priority>
     <xhtml:link rel="alternate" hreflang="zh-CN" href="https://datawhalechina.github.io/easy-vibe/zh-cn/"/>
@@ -921,7 +921,7 @@
   </url>
   <url>
     <loc>https://datawhalechina.github.io/easy-vibe/zh-cn/stage-2/backend/2.2-database-supabase/</loc>
-    <lastmod>2026-02-27T18:45:52+08:00</lastmod>
+    <lastmod>2026-03-18T09:34:06+08:00</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.8</priority>
     <xhtml:link rel="alternate" hreflang="zh-CN" href="https://datawhalechina.github.io/easy-vibe/zh-cn/stage-2/backend/2.2-database-supabase/"/>