Inconsistent behavior when re-ordering Sponsors

**Describe the bug**
When reordering Sponsor logos in the Event Dashboard, moving a sponsor twice causes odd behavior (duplication/removal).

**To Reproduce**
Steps to reproduce the behavior:
1. Go to the Event Dashboard > Add/Edit Sponsors
2. Add multiple sponsors
3. Attempt to move one sponsor two or more times
4. Reload the page and observe odd behavior

**Expected behavior**
The list should remain consistent, with the only change being the logo moved twice.

**Screenshots**

https://github.com/user-attachments/assets/5fe6fe24-0db8-46ff-a017-3b9019cbe4a8

The behavior I've been observing has been a little inconsistent. In this example, the first time, a logo is only moved once, and the behavior seems fine. The second time, the Amazon logo is moved up twice, but on reload, the Amazon Ads logo suddenly is duplicated. After manipulating the duplicated logos for a bit, I try to move the Amazon logo "down," but it actually moves to the top of the list. Finally, at the end, I reload the page and the duplicated logo has vanished.

**Device (please complete the following information):**
- OS: macOS 15.2 (24C101)
- Browser: Firefox 133.0.3 (aarch64)
- FTCLive v6.4.2

Start in the Event Dashboard's Add/Edit Sponsors screen and reproduce the issue by adding multiple sponsors, moving one twice, and reloading. Trace the sponsor ordering state and persistence from that entry point; done means repeated moves preserve the list without duplication or removal and the moved logo remains in the expected position after reload.

Written by the indexing model from the issue text.