## Describe the bug

When an MCP server is created or updated with `delegate_auth_to_upstream: true`, the value persists in PostgreSQL, but `GET /v1/mcp/server` consistently returns `delegate_auth_to_upstream: false`.

This makes the Admin UI toggle appear off after save/reload, and may cause subsequent updates to write `false` back to the database because the UI re-syncs from the GET response.

## To Reproduce

1. Run LiteLLM proxy with `STORE_MODEL_IN_DB=True` and a connected Postgres database (migration `20260513120000_add_delegate_auth_to_upstream_to_mcp_servers` applied). 2. Create or update an OAuth2 MCP server with `delegate_auth_to_upstream: true` via `POST /v1/mcp/server` or `PUT /v1/mcp/server`, or via the Admin UI. 3. Confirm the value in the database:

```sql SELECT server_name, delegate_auth_to_upstream FROM "LiteLLM_MCPServerTable"; -- delegate_auth_to_upstream = true ```

4. Fetch the server via the management API:

```bash curl -s http://localhost:4000/v1/mcp/server \ -H "Authorization: Bearer <proxy-admin-key>" ```

5. Observe that the same server returns `"delegate_auth_to_upstream": false`.

## Expected behavior

`GET /v1/mcp/server` should return the same `del…