feat(onboarding): enhance integration setup with Docker discovery, URL templating, and API key helpers

Add automatic Docker container discovery during onboarding to pre-select
and pre-fill integrations. Introduce base URL templating with subdomain/port
modes, API key settings path links, and a curated onboarding list that
hides niche integrations (GitHub, npm, Docker Hub, etc.). Prevent duplicate
widget seeding and remove the timetable widget from defaults.

apps/nextjs/src/components/integration/integration-select-grid.tsx

@@ -24,7 +24,7 @@ export const IntegrationSelectGrid = ({ onSelect, enableMockIntegration = false
   const [search, setSearch] = useState("");
   const t = useI18n();
 
-  const integrations = useMemo(() => buildSortedIntegrations(enableMockIntegration), [enableMockIntegration]);
+  const integrations = useMemo(() => buildSortedIntegrations({ enableMockIntegration }), [enableMockIntegration]);
   const filtered = useMemo(() => filterIntegrations(integrations, search), [integrations, search]);
 
   return (