feat(ST-313): add Sprint nav link to navbar when on product page

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

components/shared/nav-bar.tsx

@@ -22,6 +22,9 @@ interface NavBarProps {
 export function NavBar({ isDemo, roles }: NavBarProps) {
   const pathname = usePathname()
 
+  const productMatch = pathname.match(/^\/products\/([^/]+)/)
+  const productId = productMatch ? productMatch[1] : null
+
   const navLinks = [
     { href: '/dashboard', label: 'Producten' },
     { href: '/todos', label: "Todo's" },
@@ -56,6 +59,19 @@ export function NavBar({ isDemo, roles }: NavBarProps) {
             {link.label}
           </Link>
         ))}
+        {productId && (
+          <Link
+            href={`/products/${productId}/sprint`}
+            className={cn(
+              'px-3 py-1.5 rounded-md text-sm transition-colors',
+              pathname.includes('/sprint')
+                ? 'bg-primary-container text-primary-container-foreground font-medium'
+                : 'text-muted-foreground hover:text-foreground hover:bg-surface-container'
+            )}
+          >
+            Sprint
+          </Link>
+        )}
       </nav>
 
       {/* Rechts: rollen + instellingen + uitloggen */}