improvement(landing): scope navbar/footer shell to (shell) route group, align scoped 404s with root

Move integrations and models page routes into a `(shell)` route group so the Navbar+Footer layout wraps pages but not `not-found.tsx`. This lets scoped 404s render the same `<AuthBackground>` + Navbar treatment as the root `/` 404, instead of appearing inside the landing CTA footer.

Extract the shared 404 markup into `<NotFoundView>` so root, integrations, and models 404s share a single source of truth. Route URLs are unchanged — route groups are URL-transparent.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: waleedlatif1

apps/sim/app/(landing)/components/not-found-view.tsx

@@ -0,0 +1,40 @@
+import Link from 'next/link'
+import { getNavBlogPosts } from '@/lib/blog/registry'
+import AuthBackground from '@/app/(auth)/components/auth-background'
+import { AUTH_PRIMARY_CTA_BASE } from '@/app/(auth)/components/auth-button-classes'
+import Navbar from '@/app/(landing)/components/navbar/navbar'
+
+/**
+ * Shared 404 view used by every `not-found.tsx` under the landing surface.
+ *
+ * Rendered outside the route-group `(shell)` layout so it owns the full
+ * viewport (Navbar + AuthBackground decoration, no Footer), matching the
+ * root `/` 404 treatment.
+ */
+export default async function NotFoundView() {
+  const blogPosts = await getNavBlogPosts()
+  return (
+    <AuthBackground className='dark font-[430] font-season'>
+      <main className='relative flex min-h-full flex-col text-[var(--landing-text)]'>
+        <header className='shrink-0 bg-[var(--landing-bg)]'>
+          <Navbar blogPosts={blogPosts} />
+        </header>
+        <div className='relative z-30 flex flex-1 items-center justify-center px-4 pb-24'>
+          <div className='flex flex-col items-center gap-3'>
+            <h1 className='text-balance font-[430] font-season text-[40px] text-white leading-[110%] tracking-[-0.02em]'>
+              Page not found
+            </h1>
+            <p className='font-[430] font-season text-[color-mix(in_srgb,var(--landing-text-subtle)_60%,transparent)] text-lg leading-[125%] tracking-[0.02em]'>
+              The page you&apos;re looking for doesn&apos;t exist or has been moved.
+            </p>
+            <div className='mt-3 flex items-center gap-2'>
+              <Link href='/' className={AUTH_PRIMARY_CTA_BASE}>
+                Return to Home
+              </Link>
+            </div>
+          </div>
+        </div>
+      </main>
+    </AuthBackground>
+  )
+}

…g]/components/integration-cta-button.tsx …g]/components/integration-cta-button.tsxapps/sim/app/(landing)/integrations/[slug]/components/integration-cta-button.tsx renamed to apps/sim/app/(landing)/integrations/(shell)/[slug]/components/integration-cta-button.tsx apps/sim/app/(landing)/integrations/[slug]/components/integration-cta-button.tsx renamed to apps/sim/app/(landing)/integrations/(shell)/[slug]/components/integration-cta-button.tsx

@@ -3,9 +3,9 @@ import Image from 'next/image'
 import Link from 'next/link'
 import { notFound } from 'next/navigation'
 import { SITE_URL } from '@/lib/core/utils/urls'
-import { IntegrationCtaButton } from '@/app/(landing)/integrations/[slug]/components/integration-cta-button'
-import { IntegrationFAQ } from '@/app/(landing)/integrations/[slug]/components/integration-faq'
-import { TemplateCardButton } from '@/app/(landing)/integrations/[slug]/components/template-card-button'
+import { IntegrationCtaButton } from '@/app/(landing)/integrations/(shell)/[slug]/components/integration-cta-button'
+import { IntegrationFAQ } from '@/app/(landing)/integrations/(shell)/[slug]/components/integration-faq'
+import { TemplateCardButton } from '@/app/(landing)/integrations/(shell)/[slug]/components/template-card-button'
 import { IntegrationIcon } from '@/app/(landing)/integrations/components/integration-icon'
 import { blockTypeToIconMap } from '@/app/(landing)/integrations/data/icon-mapping'
 import integrations from '@/app/(landing)/integrations/data/integrations.json'

…ns/[slug]/components/integration-faq.tsx …l)/[slug]/components/integration-faq.tsxapps/sim/app/(landing)/integrations/[slug]/components/integration-faq.tsx renamed to apps/sim/app/(landing)/integrations/(shell)/[slug]/components/integration-faq.tsx apps/sim/app/(landing)/integrations/[slug]/components/integration-faq.tsx renamed to apps/sim/app/(landing)/integrations/(shell)/[slug]/components/integration-faq.tsx

@@ -1,28 +1,11 @@
 import type { Metadata } from 'next'
-import Link from 'next/link'
-import { AUTH_PRIMARY_CTA_BASE } from '@/app/(auth)/components/auth-button-classes'
+import NotFoundView from '@/app/(landing)/components/not-found-view'
 
 export const metadata: Metadata = {
   title: 'Page Not Found',
   robots: { index: false, follow: true },
 }
 
 export default function IntegrationsNotFound() {
-  return (
-    <div className='flex min-h-[60vh] items-center justify-center px-4 py-24'>
-      <div className='flex flex-col items-center gap-3'>
-        <h1 className='text-balance font-[430] font-season text-[40px] text-white leading-[110%] tracking-[-0.02em]'>
-          Page not found
-        </h1>
-        <p className='font-[430] font-season text-[color-mix(in_srgb,var(--landing-text-subtle)_60%,transparent)] text-lg leading-[125%] tracking-[0.02em]'>
-          The page you&apos;re looking for doesn&apos;t exist or has been moved.
-        </p>
-        <div className='mt-3 flex items-center gap-2'>
-          <Link href='/' className={AUTH_PRIMARY_CTA_BASE}>
-            Return to Home
-          </Link>
-        </div>
-      </div>
-    </div>
-  )
+  return <NotFoundView />
 }