[Auth] URLs reset in non-production branches

# Bug report <!-- ⚠️ We receive a lot of bug reports which have already been solved or discussed. If you are looking for help, please try these first: - Docs: https://docs.supabase.com - Discussions: https://github.com/supabase/supabase/discussions - Discord: https://discord.supabase.com Before opening a bug report, please verify the following: --> - [x] I confirm this is a bug with Supabase, not with my own application. - [x] I confirm I have searched the [Docs](https://docs.supabase.com), GitHub [Discussions](https://github.com/supabase/supabase/discussions), and [Discord](https://discord.supabase.com). ## Describe the bug Email confirmation redirect URLs configured in Authentication > URL Configuration get reset unexpectedly on preview branches. After configuring custom redirect URLs, they revert to `localhost:3000`, causing confirmation emails to contain incorrect redirect links. This issue occurs specifically on preview branches (not the main production branch). **Note:** This bug is difficult to reproduce on demand. The reset happens intermittently and I haven't been able to identify the exact trigger. It could be related to branch syncing, deployments, or some scheduled background process. ## To Reproduce 1. Create a preview branch in Supabase Dashboard 2. Go to Authentication > URL Configuration 3. Set custom Site URL and Redirect URLs (e.g., `https://my-preview-app.vercel.app`) 4. Save the configuration 5. Wait some time (the reset timing is unpredictable — could be hours or days) 6. Check the URL Configuration again — values have reverted to `localhost:3000` 7. Trigger a confirmation email — the redirect URL in the email points to `localhost:3000` instead of the configured URL **Important:** The exact conditions that trigger the reset are unknown. The issue has been observed multiple times but not consistently reproducible. ## Expected behavior Once configured, the Site URL and Redirect URL…