fix(privacy): de-duplicate trusted devices and handle the summary loading state

Trusted devices was mounted on both the Security section and the Privacy
dashboard. Keep it only on the Privacy dashboard, which already gathers sessions
and security activity, and drop it from the Security section. While here: the
Retention card painted an empty list while the privacy summary was loading and
on error — give it a skeleton placeholder and a one-line fallback, and align the
"What's stored" indentation with the other privacy cards.

src/components/settings/security-section/index.tsx

@@ -10,7 +10,6 @@ import { TotpCard } from "./totp-card";
 import { SecurityKeysCard, type WebauthnKeyInfo } from "./security-keys-card";
 import { PasskeyListSection } from "./passkey-list-section";
 import { PasskeyUpgradeNudge } from "./passkey-upgrade-nudge";
-import { TrustedDevicesCard } from "@/components/settings/trusted-devices-card";
 
 interface MfaStatus {
   totp: { enabled: boolean };
@@ -68,8 +67,6 @@ export function SecuritySection() {
       <SecurityKeysCard keys={status.webauthn} />
 
       <PasskeyListSection isAuthenticated={isAuthenticated} />
-
-      <TrustedDevicesCard isAuthenticated={isAuthenticated} />
     </div>
   );
 }