Fix auth redirect to use session email instead of hardcoded workspace

New users were being sent to /marks-account/projects. Now derives
workspace from the signed-in user's email so everyone lands on
their own workspace after Google OAuth.

Made-with: Cursor

app/auth/page.tsx

@@ -5,22 +5,27 @@ import { useRouter, useSearchParams } from "next/navigation";
 import { useEffect, Suspense } from "react";
 import NextAuthComponent from "@/app/components/NextAuthComponent";
 
+function deriveWorkspace(email: string): string {
+  return email.split("@")[0].toLowerCase().replace(/[^a-z0-9]+/g, "-") + "-account";
+}
+
 function AuthPageInner() {
-  const { status } = useSession();
+  const { data: session, status } = useSession();
   const router = useRouter();
   const searchParams = useSearchParams();
 
   useEffect(() => {
-    if (status === "authenticated") {
+    if (status === "authenticated" && session?.user?.email) {
       const callbackUrl = searchParams.get("callbackUrl");
       // Only follow external callbackUrls we control (Theia subdomain)
       if (callbackUrl && callbackUrl.startsWith("https://theia.vibnai.com")) {
         window.location.href = callbackUrl;
       } else {
-        router.push("/marks-account/projects");
+        const workspace = deriveWorkspace(session.user.email);
+        router.push(`/${workspace}/projects`);
       }
     }
-  }, [status, router, searchParams]);
+  }, [status, session, router, searchParams]);
 
   if (status === "loading") {
     return (