feat(landing): swap Try Demo for Get Started Free CTA in top nav (#418)

Book a Demo moves into the outline nav slot (Try Demo is removed), and a new Get Started Free primary CTA links to the docs getting-started guide in a new tab. Applies to both the desktop bar and the mobile menu.

Claude-Session: https://claude.ai/code/session_01STf4CGEkYKNwN26rMxVpn6

apps/landing/src/components/Navbar.astro

@@ -49,18 +49,18 @@ const links = [
         <span id="gh-stars" class="text-xs">{starCount}</span>
       </a>
       <a
-        href="https://demo.snapotter.com"
-        target="_blank"
-        rel="noopener noreferrer"
+        href="/contact"
         class="rounded-lg border border-border px-4 py-1.5 text-sm font-medium transition-colors hover:bg-background-alt"
       >
-        Try Demo
+        Book a Demo
       </a>
       <a
-        href="/contact"
+        href="https://docs.snapotter.com/guide/getting-started.html"
+        target="_blank"
+        rel="noopener noreferrer"
         class="btn-primary rounded-lg px-4 py-1.5 text-sm font-semibold"
       >
-        Book a Demo
+        Get Started Free
       </a>
     </div>
 
@@ -87,18 +87,18 @@ const links = [
     ))}
     <div class="mt-3 flex flex-col gap-2">
       <a
-        href="https://demo.snapotter.com"
-        target="_blank"
-        rel="noopener noreferrer"
+        href="/contact"
         class="block rounded-lg border border-border px-4 py-2 text-center text-sm font-medium"
       >
-        Try Demo
+        Book a Demo
       </a>
       <a
-        href="/contact"
+        href="https://docs.snapotter.com/guide/getting-started.html"
+        target="_blank"
+        rel="noopener noreferrer"
         class="btn-primary block rounded-lg px-4 py-2 text-center text-sm font-semibold"
       >
-        Book a Demo
+        Get Started Free
       </a>
     </div>
   </div>