feat: add GitHub link to navbar

- Add official GitHub Invertocat mark (from Drebin451 footer icon) as a
  new nav item in the default navbar, linking to https://github.com/Commit451
- Place it between Services and Book a Call (where the removed Blog link sat)
- Include it in both desktop nav and mobile menu
- Opens in a new tab with rel=noopener noreferrer and aria-label

Author: Oni

public/images/github-mark.svg

@@ -33,6 +33,9 @@ const brandHref = variant === 'default' ? '#hero' : '/';
         <a href="#work" class={`text-gray-400 ${hoverColor} transition-colors`}>Work</a>
         <a href="#about" class={`text-gray-400 ${hoverColor} transition-colors`}>About</a>
         <a href="#services" class={`text-gray-400 ${hoverColor} transition-colors`}>Services</a>
+        <a href="https://github.com/Commit451" target="_blank" rel="noopener noreferrer" aria-label="GitHub" title="GitHub" class={`flex items-center text-gray-400 ${hoverColor} transition-colors`}>
+          <img src="/images/github-mark.svg" alt="GitHub" width="20" height="20" class="w-5 h-5">
+        </a>
         <a href="https://cal.com/commit451/15min" target="_blank" rel="noopener noreferrer" class={`rounded-lg border ${borderColor} px-4 py-2 ${activeColor} ${hoverBg} transition-all`}>Book a Call</a>
       </div>
     )}
@@ -55,6 +58,9 @@ const brandHref = variant === 'default' ? '#hero' : '/';
           <a href="#work" class={`text-gray-400 ${hoverColor} transition-colors`}>Work</a>
           <a href="#about" class={`text-gray-400 ${hoverColor} transition-colors`}>About</a>
           <a href="#services" class={`text-gray-400 ${hoverColor} transition-colors`}>Services</a>
+          <a href="https://github.com/Commit451" target="_blank" rel="noopener noreferrer" aria-label="GitHub" title="GitHub" class={`flex items-center text-gray-400 ${hoverColor} transition-colors`}>
+            <img src="/images/github-mark.svg" alt="GitHub" width="20" height="20" class="w-5 h-5">
+          </a>
           <a href="https://cal.com/commit451/15min" target="_blank" rel="noopener noreferrer" class={activeColor}>Book a Call</a>
         </>
       )}