style: improve GitHub link visibility with whitesmoke default and clearer blue hover

- Change default color from accent-blue to whitesmoke for better visibility
- Add clearer light blue hover color (#66B3FF instead of dark blue)
- Add smooth color transition on hover
- Remove inline color style, use CSS class instead

templates/index.html

@@ -241,7 +241,7 @@
     <!-- Footer (hidden in print) -->
     <footer class="no-print">
         <p style="text-align: center; margin-bottom: 0.5rem;">
-            <a href="https://github.com/juanatsap/cv-site" target="_blank" rel="noopener noreferrer" style="color: var(--accent-blue); text-decoration: none; display: inline-flex; align-items: center; gap: 0.5rem;">
+            <a href="https://github.com/juanatsap/cv-site" target="_blank" rel="noopener noreferrer" class="github-repo-link" style="text-decoration: none; display: inline-flex; align-items: center; gap: 0.5rem;">
                 <iconify-icon icon="mdi:github" width="20" height="20"></iconify-icon>
                 {{if eq .Lang "es"}}Ver este proyecto en GitHub{{else}}View this project on GitHub{{end}}
             </a>