fix: show support contact message if Studio fails to load (FE-4460) (#50872)

## Summary
- Adds a fallback message ("Taking longer than expected?... contact
support@supabase.io") shown after 7s if Studio fails to fully load, for
the Next.js runtime — mirrors the existing TanStack-only
`ShellFallback`, which had no Next.js equivalent
- Fixes the support email in the existing TanStack `ShellFallback` (was
`support@supabase.com`, should be `support@supabase.io`)
- Extracts the shared copy (message, email, delay) into one file so both
fallbacks stay in sync

## Why
Linear FE-4460: users reported the Dashboard going completely blank with
no way to reach support when a JS chunk failed to load. The Next.js
runtime (the current default) had no fallback at all for this case.

## Test plan
- [ ] Normal page load: fallback never appears
- [ ] Simulated stuck boot (mount signal disabled): fallback appears
after 7s with correct copy/email, no layout bugs
- [ ] Same two checks on the TanStack runtime
(`STUDIO_FRAMEWORK=tanstack`)
- [ ] `pnpm --filter studio run typecheck` / `lint:ratchet` pass

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Added a loading fallback that appears if the app takes too long to
load, with guidance to clear browser cookies and reload.
* On self-hosted platforms, the fallback includes a support contact
link.
  * The fallback is automatically hidden once the app loads.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

apps/studio/components/interfaces/App/ShellFallback.tsx

@@ -1,5 +1,10 @@
 import { LogoLoader } from 'ui'
 
+import {
+  BOOT_FALLBACK_MESSAGE,
+  BOOT_FALLBACK_REVEAL_DELAY_SECONDS,
+  BOOT_FALLBACK_SUPPORT_EMAIL,
+} from '@/lib/boot-fallback-copy'
 import { IS_PLATFORM } from '@/lib/constants'
 
 // Baked into the prerendered SPA shell (_shell.html) — this is the static HTML
@@ -15,7 +20,7 @@ export function ShellFallback() {
         #studio-shell-help {
           visibility: hidden;
           opacity: 0;
-          animation: studio-shell-help-reveal 0.3s ease-out 7s forwards;
+          animation: studio-shell-help-reveal 0.3s ease-out ${BOOT_FALLBACK_REVEAL_DELAY_SECONDS}s forwards;
         }
         @keyframes studio-shell-help-reveal {
           to {
@@ -40,13 +45,13 @@ export function ShellFallback() {
           data-nosnippet=""
           className="max-w-md text-center text-sm text-foreground-light"
         >
-          Taking longer than expected? Try clearing your browser cookies and reloading the page.
+          {BOOT_FALLBACK_MESSAGE}
           {IS_PLATFORM && (
             <>
               {' '}
               If the problem persists, contact{' '}
-              <a href="mailto:support@supabase.com" className="underline">
-                support@supabase.com
+              <a href={`mailto:${BOOT_FALLBACK_SUPPORT_EMAIL}`} className="underline">
+                {BOOT_FALLBACK_SUPPORT_EMAIL}
               </a>
               .
             </>

apps/studio/components/ui/BootTimeoutFallback/BootTimeoutFallback.tsx

@@ -0,0 +1,75 @@
+import {
+  BOOT_FALLBACK_MESSAGE,
+  BOOT_FALLBACK_REVEAL_DELAY_SECONDS,
+  BOOT_FALLBACK_SUPPORT_EMAIL,
+} from '@/lib/boot-fallback-copy'
+import { IS_PLATFORM } from '@/lib/constants'
+
+const FALLBACK_ID = 'studio-boot-fallback'
+
+// Next.js equivalent of the TanStack build's ShellFallback (see
+// components/interfaces/App/ShellFallback.tsx): a safety net for a stuck
+// chunk load (FE-4460). Next always server-renders real page content into
+// <Main />, so — unlike TanStack's ClientOnly fallback, which shows nothing
+// until hydration — this can't be a full-screen overlay shown by default; it
+// has to reveal itself only once it's clear the page is actually stuck.
+//
+// The reveal is pure CSS (a delayed animation), not a JS timer, so it still
+// fires even if every JS chunk fails to load. Hiding it on a successful
+// mount necessarily needs JS — see `clearBootTimeoutFallback` — but a
+// missed hide is harmless: the reveal only starts after
+// BOOT_FALLBACK_REVEAL_DELAY_SECONDS, by which point a successful mount has
+// long since hidden it.
+export function BootTimeoutFallback() {
+  return (
+    <>
+      <style>{`
+        #${FALLBACK_ID} {
+          position: fixed;
+          inset: 0;
+          z-index: 9999;
+          display: flex;
+          align-items: center;
+          justify-content: center;
+          padding: 24px;
+          background: #1c1c1c;
+          pointer-events: none;
+          visibility: hidden;
+          opacity: 0;
+          animation: studio-boot-fallback-reveal 0.3s ease-out ${BOOT_FALLBACK_REVEAL_DELAY_SECONDS}s forwards;
+        }
+        #${FALLBACK_ID} p {
+          color: #fff;
+          font-family: sans-serif;
+          font-size: 14px;
+          text-align: center;
+        }
+        @keyframes studio-boot-fallback-reveal {
+          to {
+            visibility: visible;
+            opacity: 1;
+            pointer-events: auto;
+          }
+        }
+      `}</style>
+      <div id={FALLBACK_ID}>
+        <p>
+          {BOOT_FALLBACK_MESSAGE}
+          {IS_PLATFORM && (
+            <>
+              {' '}
+              If the problem persists, contact{' '}
+              <a href={`mailto:${BOOT_FALLBACK_SUPPORT_EMAIL}`}>{BOOT_FALLBACK_SUPPORT_EMAIL}</a>.
+            </>
+          )}
+        </p>
+      </div>
+    </>
+  )
+}
+
+/** Call once the app has actually mounted, to hide the fallback above. */
+export function clearBootTimeoutFallback() {
+  const el = document.getElementById(FALLBACK_ID)
+  if (el) el.style.display = 'none'
+}

apps/studio/lib/boot-fallback-copy.ts

@@ -0,0 +1,6 @@
+// Shared between ShellFallback (TanStack) and BootTimeoutFallback (Next.js) —
+// same "stuck loading" message, different markup per runtime (see FE-4460).
+export const BOOT_FALLBACK_REVEAL_DELAY_SECONDS = 7
+export const BOOT_FALLBACK_SUPPORT_EMAIL = 'support@supabase.io'
+export const BOOT_FALLBACK_MESSAGE =
+  'Taking longer than expected? Try clearing your browser cookies and reloading the page.'

apps/studio/pages/_app.tsx

@@ -48,6 +48,7 @@ import { MonacoThemeProvider } from '@/components/interfaces/App/MonacoThemeProv
 import { RouteValidationWrapper } from '@/components/interfaces/App/RouteValidationWrapper'
 import { MainScrollContainerProvider } from '@/components/layouts/MainScrollContainerContext'
 import { BannerStackProvider } from '@/components/ui/BannerStack/BannerStackProvider'
+import { clearBootTimeoutFallback } from '@/components/ui/BootTimeoutFallback/BootTimeoutFallback'
 import { GlobalErrorBoundaryState } from '@/components/ui/ErrorBoundary/GlobalErrorBoundaryState'
 import { GlobalShortcuts } from '@/components/ui/GlobalShortcuts/GlobalShortcuts'
 import { getCLIReleaseVersion } from '@/data/misc/cli-release-version-query'
@@ -157,6 +158,10 @@ function CustomApp({ Component, pageProps }: AppPropsWithLayout) {
 
   useThemeSandbox()
 
+  useEffect(() => {
+    clearBootTimeoutFallback()
+  }, [])
+
   const isTestEnv = process.env.NEXT_PUBLIC_NODE_ENV === 'test'
 
   // [Joshen] Should target hosted staging, local dev, and local CLI only

apps/studio/pages/_document.tsx

@@ -1,5 +1,6 @@
 import Document, { DocumentContext, Head, Html, Main, NextScript } from 'next/document'
 
+import { BootTimeoutFallback } from '@/components/ui/BootTimeoutFallback/BootTimeoutFallback'
 import { inter, manrope, sourceCodePro } from '@/fonts'
 
 class MyDocument extends Document {
@@ -14,6 +15,7 @@ class MyDocument extends Document {
       <Html lang="en">
         <Head />
         <body className={`${inter.variable} ${manrope.variable} ${sourceCodePro.variable}`}>
+          <BootTimeoutFallback />
           <Main />
           <NextScript />
         </body>