fix(favicon): resolve metadata at request time, fully honor whitelabel favicon

Addresses the second round of review findings on PR #5588:

- Cursor (High): app/layout.tsx exported a static `export const metadata =
  generateBrandedMetadata()`. Next.js treats a static metadata object as
  truly constant (eligible for build-time resolution on any
  statically-rendered route sharing the layout), so it doesn't know this
  one secretly depends on process.env via getDeploymentEnv() - same
  bake-in risk already fixed for next.config.ts. Converted to
  generateMetadata(), the documented way to force per-request resolution.

- Greptile (P1): the earlier whitelabel fallback fixed the *tint* but not
  the underlying precedence gap - Sim's exact-size PNG/apple entries were
  still emitted alongside the tenant's generic sizes:'any' entry, and
  browsers can prefer the more specific size match. Now the tenant
  favicon fully replaces every icon slot instead of being appended
  alongside Sim's.

- Cursor (Medium): app/api/favicon/route.ts never checked
  brand.faviconUrl, so a whitelabeled dev/staging deployment still served
  Sim's tinted icon at the legacy /favicon.ico path. Now checks
  brand.faviconUrl first, matching generateBrandedMetadata()'s
  precedence.

Author: waleedlatif1

apps/sim/app/api/favicon/route.ts

@@ -1,6 +1,7 @@
 import { type NextRequest, NextResponse } from 'next/server'
 import { getDeploymentEnv } from '@/lib/core/config/env-flags'
 import { withRouteHandler } from '@/lib/core/utils/with-route-handler'
+import { getBrandConfig } from '@/ee/whitelabeling/branding'
 
 export const dynamic = 'force-dynamic'
 
@@ -21,8 +22,13 @@ const FAVICON_DESTINATIONS: Record<ReturnType<typeof getDeploymentEnv>, string>
  * here, at request time, not in `next.config.ts`, which only runs once during
  * that shared build and would freeze whichever tier happened to be active
  * then (never the tier the container actually ends up running as).
+ *
+ * A whitelabeled deployment's own favicon always wins here too, matching
+ * `generateBrandedMetadata()` (`ee/whitelabeling/metadata.ts`) — a tenant on
+ * a dev/staging environment should never see Sim's internal tinted mark.
  */
 export const GET = withRouteHandler(async (request: NextRequest) => {
-  const destination = FAVICON_DESTINATIONS[getDeploymentEnv()]
+  const brand = getBrandConfig()
+  const destination = brand.faviconUrl || FAVICON_DESTINATIONS[getDeploymentEnv()]
   return NextResponse.redirect(new URL(destination, request.url))
 })

apps/sim/app/layout.tsx

@@ -24,7 +24,19 @@ export const viewport: Viewport = {
   ],
 }
 
-export const metadata: Metadata = generateBrandedMetadata()
+/**
+ * Not a static `export const metadata` object: {@link generateBrandedMetadata}
+ * reads `getDeploymentEnv()` for the favicon set, which depends on
+ * `process.env` being populated by `bootstrap.ts`'s runtime secrets load. A
+ * static object is resolved once at module-evaluation time and Next.js treats
+ * it as truly constant (eligible for build-time resolution on any
+ * statically-rendered route sharing this layout) — `generateMetadata()`
+ * forces the same per-request resolution `app/api/favicon/route.ts` already
+ * uses.
+ */
+export function generateMetadata(): Metadata {
+  return generateBrandedMetadata()
+}
 
 const GTM_ID = 'GTM-T7PHSRX5' as const
 const GA_ID = 'G-DR7YBE70VS' as const

apps/sim/ee/whitelabeling/metadata.ts

@@ -139,23 +139,22 @@ export function generateBrandedMetadata(override: Partial<Metadata> = {}): Metad
     },
     manifest: '/manifest.webmanifest',
     icons: {
-      icon: [
-        ...(brand.faviconUrl ? [] : [{ url: icons.svg, type: 'image/svg+xml', sizes: 'any' }]),
-        { url: icons.favicon16, sizes: '16x16', type: 'image/png' },
-        { url: icons.favicon32, sizes: '32x32', type: 'image/png' },
-        {
-          url: icons.android192,
-          sizes: '192x192',
-          type: 'image/png',
-        },
-        {
-          url: icons.android512,
-          sizes: '512x512',
-          type: 'image/png',
-        },
-        ...(brand.faviconUrl ? [{ url: brand.faviconUrl, sizes: 'any', type: 'image/png' }] : []),
-      ],
-      apple: icons.apple,
+      // A whitelabeled deployment only ever supplies one favicon URL (no
+      // multi-size set of its own) - emitting Sim's exact-size PNG/apple
+      // entries alongside it would let browsers prefer those more specific
+      // sizes over the tenant's generic `sizes: 'any'` entry, showing Sim
+      // branding instead. So the tenant favicon fully replaces every slot
+      // rather than being appended to Sim's.
+      icon: brand.faviconUrl
+        ? [{ url: brand.faviconUrl, sizes: 'any', type: 'image/png' }]
+        : [
+            { url: icons.svg, type: 'image/svg+xml', sizes: 'any' },
+            { url: icons.favicon16, sizes: '16x16', type: 'image/png' },
+            { url: icons.favicon32, sizes: '32x32', type: 'image/png' },
+            { url: icons.android192, sizes: '192x192', type: 'image/png' },
+            { url: icons.android512, sizes: '512x512', type: 'image/png' },
+          ],
+      apple: brand.faviconUrl || icons.apple,
       shortcut: brand.faviconUrl || icons.svg,
     },
     appleWebApp: {