feat(web): account data export + sidebar rebrand to "Account"

Step 16 (account / profile) — landed smaller than scoped because turbo-
starter already ships the full /dashboard/settings flow (avatar, name,
email, language, delete-account) and BetterAuth handles security +
sessions out of the box. Reuses that surface; adds the claudemesh-
specific bits only.

- GET /api/my/export — returns a JSON bundle of the user's profile,
  meshes they own, meshes they belong to, invites they've issued, and
  audit events from their OWNED meshes (privacy: don't leak events
  from meshes merely joined). Limited to 5k audit rows.
- ExportData component on /dashboard/settings — button downloads the
  bundle as claudemesh-export-<userId>-<YYYY-MM-DD>.json client-side.
- Sidebar (user group) "settings" label swapped to "account" to match
  the Step 16 naming. Same /dashboard/settings route, same existing
  i18n key ("account" was already in common.json).

No schema changes: user.name (BetterAuth) IS the mesh display name.
meshMember.displayName is the per-join override that lands from the
CLI at registration time.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/src/modules/user/settings/general/export-data.tsx

@@ -0,0 +1,53 @@
+"use client";
+
+import { useState } from "react";
+
+import { Button } from "@turbostarter/ui-web/button";
+
+export const ExportData = () => {
+  const [loading, setLoading] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+
+  const onExport = async () => {
+    setLoading(true);
+    setError(null);
+    try {
+      const res = await fetch("/api/my/export", { credentials: "include" });
+      if (!res.ok) {
+        throw new Error(`Export failed (${res.status})`);
+      }
+      const data = (await res.json()) as { user: { id: string } };
+      const blob = new Blob([JSON.stringify(data, null, 2)], {
+        type: "application/json",
+      });
+      const url = URL.createObjectURL(blob);
+      const date = new Date().toISOString().slice(0, 10);
+      const a = document.createElement("a");
+      a.href = url;
+      a.download = `claudemesh-export-${data.user.id}-${date}.json`;
+      document.body.appendChild(a);
+      a.click();
+      a.remove();
+      URL.revokeObjectURL(url);
+    } catch (e) {
+      setError(e instanceof Error ? e.message : "Export failed");
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  return (
+    <div className="rounded-lg border p-5">
+      <h3 className="mb-1 font-medium">Export your data</h3>
+      <p className="text-muted-foreground mb-4 text-sm">
+        Download a JSON file with your profile, meshes you own, meshes you
+        joined, invites you&apos;ve issued, and audit events from your owned
+        meshes. Read-only.
+      </p>
+      <Button onClick={onExport} disabled={loading} variant="outline" size="sm">
+        {loading ? "Preparing…" : "Download export"}
+      </Button>
+      {error && <p className="text-destructive mt-2 text-sm">{error}</p>}
+    </div>
+  );
+};