Problem

• invitation_detail_page.php always showed the first 2 transfers regardless of the page,
  because it never passed offset or limit to transfers_table.
• Clicking "next" navigated to a URL without guest_id, causing "guest not found" error.

Changes

• templates/invitation_detail_page.php: read offset from GET params, slice transfers
  in PHP, pass limit=10 and offset to transfers_table. Shows 10 transfers per page.
• templates/transfers_table.php: preserve guest_id in pagination base URL so next/prev
  links don't lose the guest context.