feat(dashboard): add one-time Stack Auth → Hexclave rebrand modal

Announces the rebrand to authenticated dashboard users whose
signedUpAt predates 2026-05-27 UTC (the rebrand cutoff). Brand-new
users signing up after the cutoff already land on Hexclave-branded
surfaces and don't see the modal.

- Modal lives in the protected dashboard layout via
  apps/dashboard/src/app/(main)/(protected)/layout-client.tsx so it
  surfaces on any logged-in route once per browser.
- Gated on useUser({ or: "return-null" }) + signedUpAt < cutoff, so
  it never triggers a sign-in redirect for guests and never shows for
  post-rebrand signups.
- Dismissal (button, X, overlay, Escape) routes through onOpenChange
  and writes "hexclave-rebrand-modal-dismissed" to localStorage so it
  never re-appears for that browser.
- Illustration uses the existing Stack Auth logo (logo.svg /
  logo-bright.svg for dark mode) and the Hexclave benzene mark saved
  to public/hexclave-icon.svg.
- Copy links app.hexclave.com and docs.hexclave.com/migration.

Screenshot: .github/assets/hexclave-rebrand-modal.png

apps/dashboard/public/hexclave-icon.svg

@@ -0,0 +1,26 @@
+<svg width="48" height="48" viewBox="0 0 48 48" fill="none" xmlns="http://www.w3.org/2000/svg">
+  <defs>
+    <linearGradient id="neon-grad" x1="4" y1="4" x2="44" y2="44" gradientUnits="userSpaceOnUse">
+      <stop offset="0%" stop-color="#00FFFF" />
+      <stop offset="50%" stop-color="#3B82F6" />
+      <stop offset="100%" stop-color="#8B5CF6" />
+    </linearGradient>
+    <filter id="glow" x="-50%" y="-50%" width="200%" height="200%">
+      <feGaussianBlur stdDeviation="1.5" result="blur1" />
+      <feGaussianBlur stdDeviation="3.5" result="blur2" />
+      <feMerge>
+        <feMergeNode in="blur2" />
+        <feMergeNode in="blur1" />
+        <feMergeNode in="SourceGraphic" />
+      </feMerge>
+    </filter>
+    <g id="benzene-mark">
+      <path d="M 24 4 L 41.32 14 L 41.32 34 L 24 44 L 6.68 34 L 6.68 14 Z" fill="none" stroke="url(#neon-grad)" stroke-width="3" stroke-linejoin="miter" />
+      <path d="M 11 16.87 L 14 15.13 L 14 32.87 L 11 31.13 Z" fill="url(#neon-grad)" />
+      <path d="M 11 16.87 L 14 15.13 L 14 32.87 L 11 31.13 Z" fill="url(#neon-grad)" transform="rotate(120 24 24)" />
+      <path d="M 11 16.87 L 14 15.13 L 14 32.87 L 11 31.13 Z" fill="url(#neon-grad)" transform="rotate(240 24 24)" />
+    </g>
+  </defs>
+  <use href="#benzene-mark" filter="url(#glow)" opacity="0.75" />
+  <use href="#benzene-mark" />
+</svg>

apps/dashboard/src/app/(main)/(protected)/layout-client.tsx

@@ -3,6 +3,7 @@
 import Loading from "@/app/loading";
 import { CursorBlastEffect } from "@stackframe/dashboard-ui-components";
 import { ConfigUpdateDialogProvider } from "@/lib/config-update";
+import { HexclaveRebrandModal } from "@/components/hexclave-rebrand-modal";
 import { getPublicEnvVar } from '@/lib/env';
 import { useStackApp, useUser } from "@stackframe/stack";
 import { LOCAL_EMULATOR_ADMIN_EMAIL, LOCAL_EMULATOR_ADMIN_PASSWORD } from "@stackframe/stack-shared/dist/local-emulator";
@@ -60,6 +61,7 @@ export default function LayoutClient({ children }: { children: React.ReactNode }
     return (
       <ConfigUpdateDialogProvider>
         <CursorBlastEffect />
+        <HexclaveRebrandModal />
         {children}
       </ConfigUpdateDialogProvider>
     );

apps/dashboard/src/components/hexclave-rebrand-modal.tsx

@@ -0,0 +1,176 @@
+"use client";
+
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogFooter,
+  DialogHeader,
+  DialogTitle,
+} from "@/components/ui/dialog";
+import { Button } from "@/components/ui/button";
+import { useUser } from "@stackframe/stack";
+import Image from "next/image";
+import { useEffect, useState } from "react";
+
+const STORAGE_KEY = "hexclave-rebrand-modal-dismissed";
+const MIGRATION_DOCS_URL = "https://docs.hexclave.com/migration";
+
+// Users who signed up before this instant predate the Stack Auth → Hexclave
+// rebrand and are the only ones who benefit from the announcement. Anyone
+// signing up after this already lands on a Hexclave-branded experience and
+// has no "Stack Auth" mental model to update — no point telling them.
+const REBRAND_CUTOFF = new Date("2026-05-27T00:00:00.000Z");
+
+/**
+ * One-time informational modal announcing the Stack Auth → Hexclave rebrand.
+ *
+ * Only renders for a logged-in user who signed up before {@link REBRAND_CUTOFF}.
+ * On any dismissal (confirm button, close button, overlay click, or Escape)
+ * writes `STORAGE_KEY` to localStorage so the modal never re-appears for that
+ * browser.
+ */
+export function HexclaveRebrandModal() {
+  // `or: "return-null"` keeps this from triggering the sign-in redirect when
+  // it's rendered above the auth boundary — we simply opt out for guests.
+  const user = useUser({ or: "return-null" });
+  const isPreRebrandUser = user != null && user.signedUpAt < REBRAND_CUTOFF;
+  const [open, setOpen] = useState(false);
+
+  // Read localStorage after hydration to avoid SSR mismatch — render closed
+  // on the server and only open if we know the user hasn't dismissed it.
+  useEffect(() => {
+    if (!isPreRebrandUser) return;
+    try {
+      const dismissed = localStorage.getItem(STORAGE_KEY);
+      if (dismissed !== "true") {
+        setOpen(true);
+      }
+    } catch {
+      // localStorage can throw in private-mode / sandboxed iframes; treat
+      // unavailable storage as "already dismissed" so we don't spam users
+      // who can't persist the dismissal anyway.
+    }
+  }, [isPreRebrandUser]);
+
+  const dismiss = () => {
+    try {
+      localStorage.setItem(STORAGE_KEY, "true");
+    } catch {
+      // see above — best-effort write
+    }
+    setOpen(false);
+  };
+
+  if (!isPreRebrandUser) return null;
+
+  return (
+    <Dialog
+      open={open}
+      onOpenChange={(next) => {
+        if (!next) dismiss();
+      }}
+    >
+      <DialogContent className="max-w-md">
+        <DialogHeader>
+          <RebrandIllustration />
+          <DialogTitle className="text-center text-xl pt-2">
+            Stack Auth is now Hexclave
+          </DialogTitle>
+          <DialogDescription className="text-center">
+            We&apos;re rebranding! Same product, same team, new home at{" "}
+            <a
+              href="https://app.hexclave.com"
+              target="_blank"
+              rel="noopener noreferrer"
+              className="font-medium underline underline-offset-2 hover:text-foreground"
+            >
+              app.hexclave.com
+            </a>
+            . For more info on how to update your project, read our{" "}
+            <a
+              href={MIGRATION_DOCS_URL}
+              target="_blank"
+              rel="noopener noreferrer"
+              className="font-medium underline underline-offset-2 hover:text-foreground"
+            >
+              migration guide
+            </a>
+            .
+          </DialogDescription>
+        </DialogHeader>
+        <DialogFooter className="sm:justify-center pt-6">
+          <Button onClick={dismiss} className="min-w-32">
+            Got it
+          </Button>
+        </DialogFooter>
+      </DialogContent>
+    </Dialog>
+  );
+}
+
+/**
+ * Stack Auth mark (faded) → arrow → Hexclave benzene mark. Both logos are
+ * served from `/public` so they match the canonical brand assets.
+ */
+function RebrandIllustration() {
+  return (
+    <div
+      className="flex justify-center items-center gap-4 pb-2"
+      aria-hidden="true"
+    >
+      {/* Stack Auth: served light & dark variants depending on theme */}
+      <Image
+        src="/logo.svg"
+        alt=""
+        width={48}
+        height={48}
+        aria-hidden
+        className="h-12 w-auto opacity-50 block dark:hidden"
+      />
+      <Image
+        src="/logo-bright.svg"
+        alt=""
+        width={48}
+        height={48}
+        aria-hidden
+        className="h-12 w-auto opacity-60 hidden dark:block"
+      />
+
+      {/* Arrow — bridge between the two marks */}
+      <svg
+        width="40"
+        height="14"
+        viewBox="0 0 40 14"
+        fill="none"
+        xmlns="http://www.w3.org/2000/svg"
+        className="text-muted-foreground"
+      >
+        <path
+          d="M2 7 L34 7"
+          stroke="currentColor"
+          strokeWidth="2"
+          strokeLinecap="round"
+        />
+        <path
+          d="M28 1 L34 7 L28 13"
+          stroke="currentColor"
+          strokeWidth="2"
+          strokeLinecap="round"
+          strokeLinejoin="round"
+          fill="none"
+        />
+      </svg>
+
+      {/* Hexclave benzene mark — gradient + glow filter, theme-agnostic */}
+      <Image
+        src="/hexclave-icon.svg"
+        alt=""
+        width={56}
+        height={56}
+        aria-hidden
+        className="h-14 w-14"
+      />
+    </div>
+  );
+}