Sign in is the default: the landing names the account, and an admin lands on /admin

docker/frontend/src/App.tsx

@@ -290,10 +290,13 @@ export function Workspace() {
   // Recipes made in this session, guest ones included. A guest's copy lives
   // here and nowhere else, so reloading the page is what deletes it.
   const [created, setCreated] = useState<Recipe[]>([]);
-  // null = closed. /app?auth=1 opens the studio's dialog straight on the sign-up
-  // tab; the landing page runs the same dialog in place instead of linking here.
-  const [authMode, setAuthMode] = useState<'login' | 'signup' | null>(() =>
-    (new URLSearchParams(window.location.search).has('auth') ? 'signup' : null));
+  // null = closed. /app?auth=1 opens the studio's dialog straight on the sign-in
+  // tab (sign-in is the default; ?auth=signup asks for the other one); the
+  // landing page runs the same dialog in place instead of linking here.
+  const [authMode, setAuthMode] = useState<'login' | 'signup' | null>(() => {
+    const asked = new URLSearchParams(window.location.search).get('auth');
+    return asked ? (asked === 'signup' ? 'signup' : 'login') : null;
+  });
 
   const renderToken = useRef(0);
   // Which previewMax the bytes in previewBytes were made at, so the upgrade