docs(terms): match the export window to the cleanup the product runs

Termination promised thirty days of export while the storage cleanup
deletes fifteen days after billing access ends, so the product could
delete content the terms still covered. Fifteen is the window that is
actually enforced, in lib/billing.ts.

The same sentence also promised content would stay available for export,
which it does not: access ends with billing, so a user inside the window
cannot reach their own footage. It now says to ask us for a copy instead
of implying the export is self-service.

app/terms/page.tsx

@@ -274,8 +274,9 @@ export default function TermsOfServicePage() {
             </p>
             <p className="mt-3">
               Except where the law requires otherwise or the content itself is unlawful, your User
-              Content will remain available for export for thirty (30) days after termination, after
-              which it may be permanently deleted.
+              Content will remain available for export for fifteen (15) days after termination,
+              after which it may be permanently deleted. Write to us within that window if you need
+              a copy and can no longer reach it yourself.
             </p>
             <p className="mt-3">
               You may cancel your account at any time through your billing settings or by contacting