Add Kupujem Prodajem purchase link to homepage

- Added prominent call-to-action button between logo and inventory table
- Styled with green gradient and hover effects
- Includes purchase and external link icons
- Opens in new tab with proper security attributes
- Tracks clicks with Matomo analytics
- Responsive design with smooth transitions

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/page.tsx

@@ -144,6 +144,25 @@ export default function Home() {
           </button>
         </div>
         
+        {/* Kupujem Prodajem Link */}
+        <div className="flex justify-center mb-8">
+          <a 
+            href="https://www.kupujemprodajem.com/kompjuteri-desktop/3d-stampaci-i-oprema/originalni-bambu-lab-filamenti-na-stanju/oglas/182256246"
+            target="_blank"
+            rel="noopener noreferrer"
+            onClick={() => trackEvent('External Link', 'Kupujem Prodajem', 'Homepage')}
+            className="inline-flex items-center gap-2 px-6 py-3 bg-gradient-to-r from-green-500 to-green-600 hover:from-green-600 hover:to-green-700 text-white font-semibold rounded-lg shadow-lg hover:shadow-xl transition-all duration-200 transform hover:scale-105"
+          >
+            <svg className="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 8c-1.657 0-3 .895-3 2s1.343 2 3 2 3 .895 3 2-1.343 2-3 2m0-8c1.11 0 2.08.402 2.599 1M12 8V7m0 1v8m0 0v1m0-1c-1.11 0-2.08-.402-2.599-1M21 12a9 9 0 11-18 0 9 9 0 0118 0z" />
+            </svg>
+            Kupi na Kupujem Prodajem
+            <svg className="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M10 6H6a2 2 0 00-2 2v10a2 2 0 002 2h10a2 2 0 002-2v-4M14 4h6m0 0v6m0-6L10 14" />
+            </svg>
+          </a>
+        </div>
+        
         <FilamentTableV2 
           key={resetKey}
           filaments={filaments}