Complete Stackless parity: Activity, Deploy, Settings, header desc

- Add project description line to project header (from productVision)
- Sidebar: add Activity nav item (Projects / Activity / Settings)
- New Activity page: timeline feed with type filters (Atlas/Builds/Deploys/You)
- New Activity layout using VIBNSidebar
- Rewrite Deploy tab: Project URLs, Custom Domain, Env Vars, Deploy History
  — fully Stackless style, real data from project API, no more MOCK_PROJECT
- Rewrite Project Settings tab: remove all Firebase refs (db, auth, Firestore)
  — General (name/description), Repo link, Collaborators, Export JSON/PDF,
  — Danger Zone with double-confirm delete
  — uses /api/projects/[id] PATCH for saves

Made-with: Cursor

app/[workspace]/activity/layout.tsx

@@ -0,0 +1,20 @@
+"use client";
+
+import { VIBNSidebar } from "@/components/layout/vibn-sidebar";
+import { useParams } from "next/navigation";
+import { ReactNode } from "react";
+import { Toaster } from "sonner";
+
+export default function ActivityLayout({ children }: { children: ReactNode }) {
+  const params = useParams();
+  const workspace = params.workspace as string;
+  return (
+    <>
+      <div style={{ display: "flex", height: "100vh", background: "#f6f4f0", overflow: "hidden" }}>
+        <VIBNSidebar workspace={workspace} />
+        <main style={{ flex: 1, overflow: "auto" }}>{children}</main>
+      </div>
+      <Toaster position="top-center" />
+    </>
+  );
+}