Fix TypeError: unusable in doubleKnock redirect handling

Fixed inconsistent request body handling in the second redirect path
of doubleKnock() function. Changed from request.clone().body to
await request.clone().arrayBuffer() to prevent body consumption issues
that caused "TypeError: unusable" errors during HTTP signature retry
attempts with redirects.

Also replaced destructuring with explicit property copying to ensure
proper Request constructor behavior.

Closes https://github.com/fedify-dev/fedify/issues/294



Co-Authored-By: Claude <noreply@anthropic.com>