fix: keep /admin reachable while setup is required (#392)

The root layout replaced the entire app with the SetupScreen whenever
the config was incomplete (missing gallery.yaml or Immich credentials)
— including /admin, which lives under the same root layout. That locked
users out of the very tool that fixes an incomplete configuration.

The middleware now forwards the request pathname via an x-pathname
header, and the root layout skips the setup screen for admin paths, so
/admin renders normally (login when ADMIN_PASSWORD is set, the
enable-hint otherwise) while every other route keeps showing the setup
instructions.

Fixes #326

Co-authored-by: ralksta <ralksta@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

app/layout.tsx

@@ -5,6 +5,7 @@
  */
 
 import type { Metadata } from 'next';
+import { headers } from 'next/headers';
 import Link from 'next/link';
 import './globals.css';
 import { SubpageNav } from '@/components/SubpageNav';
@@ -13,6 +14,7 @@ import { ScrollToTop } from '@/components/ScrollToTop';
 import { Footer } from '@/components/Footer';
 import { SetupScreen } from '@/components/SetupScreen';
 import { getConfig, getGoogleFontsUrl, AppConfig } from '@/lib/config';
+import { isAdminPath } from '@/lib/admin/paths';
 // DevToolbarLoader is a Client Component (ssr: false is only allowed there)
 import { DevToolbarLoader } from '@/components/DevToolbarLoader';
 
@@ -47,7 +49,7 @@ export async function generateMetadata(): Promise<Metadata> {
   };
 }
 
-export default function RootLayout({ children }: { children: React.ReactNode }) {
+export default async function RootLayout({ children }: { children: React.ReactNode }) {
   const config = getConfig();
   const { theme } = config;
   const fontsUrl = getGoogleFontsUrl(theme);
@@ -63,7 +65,10 @@ export default function RootLayout({ children }: { children: React.ReactNode })
     '--radius-lg': `${theme.radius * 2}px`,
   };
 
-  if ((config as AppConfig & { needsSetup?: boolean }).needsSetup) {
+  // /admin stays reachable during setup — it is the tool that completes the
+  // setup, so the setup screen must not lock it out (#326).
+  const pathname = (await headers()).get('x-pathname');
+  if ((config as AppConfig & { needsSetup?: boolean }).needsSetup && !isAdminPath(pathname)) {
     return (
       <html lang="en" suppressHydrationWarning>
         <body>