Claim legacy Stitchdown Patina Thunderdome submissions

Let users request ownership of legacy Stitchdown Patina Thunderdome submissions that were created before Patina Project handled the submission flow.

Some older Thunderdome submissions exist on Patina but are not connected to the right user account. A claim flow would help users reconnect those historic submissions to their current account without contacting support for each case.

This would make legacy Thunderdome submissions easier to preserve, manage, and view from the correct account.