feat: add actionable CTAs to all dashboard empty states

- Campaigns: "Build a UTM URL" opens UTM builder modal directly
- Pages/Referrers/Locations/Technology: "Install tracking script"
  links to /installation
- Matches existing CTA pattern from GoalStats

components/dashboard/Campaigns.tsx

@@ -206,13 +206,13 @@ export default function Campaigns({ siteId, dateRange, filters, onFilter }: Camp
               <p className="text-sm text-neutral-500 dark:text-neutral-400 max-w-xs">
                 Add UTM parameters to your links to see campaign performance here.
               </p>
-              <Link
-                href="/installation"
-                className="inline-flex items-center gap-2 text-sm font-medium text-brand-orange hover:text-brand-orange/90 hover:underline focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-brand-orange/20 rounded"
+              <button
+                onClick={() => setIsBuilderOpen(true)}
+                className="inline-flex items-center gap-2 text-sm font-medium text-brand-orange hover:text-brand-orange/90 hover:underline focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-brand-orange/20 rounded cursor-pointer"
               >
-                Learn more
+                Build a UTM URL
                 <ArrowRightIcon className="w-4 h-4" />
-              </Link>
+              </button>
             </div>
           )}
         </div>