## Why
Custom providers with gateway OAuth and an explicit model catalog should be able to discover models without an API key or API key model discovery enabled.
## What changed
- Enable catalog refreshes for custom gateway providers when `model_catalog_url` and `base_url` have the same origin.
- Reuse gateway credentials without starting an interactive login during catalog refreshes.
- Keep an unrelated saved API key from making gateway catalog discovery depend on the API key discovery setting.
## Testing
Add an app-server test for discovering a gateway catalog after OAuth login with no API key. Update coverage for catalog invalidation after gateway credentials require login, including across manager restarts, with API key discovery disabled.
GitOrigin-RevId: b133c428cb45a9037e4b2ef13ff2f9473ed96636