### Check for existing issues

- [x] I have searched the existing issues and checked that my issue is not a duplicate.

### What happened?

`POST /team/update` with `model_max_budget` returns 200 but stores `{}` (empty object) in the database. The field is silently discarded.

For comparison, `POST /user/update` with the same field persists correctly — so the field works at the user level but not at the team level.

Note: This is separate from the existing issue [#25799](https://github.com/BerriAI/litellm/issues/25799) which covers `model_max_budget` not enforcing on keys. This bug is about the field not even being writable at the team level.

### Steps to Reproduce

1. Create a team: ```bash curl -X POST /team/new \ -H "Authorization: Bearer $MASTER_KEY" \ -H "Content-Type: application/json" \ -d '{"team_id": "test"}' ```

2. Set `model_max_budget` on the team: ```bash curl -X POST /team/update \ -H "Authorization: Bearer $MASTER_KEY" \ -H "Content-Type: application/json" \ -d '{"team_id": "test", "model_max_budget": {"gpt-4": 10.0}}' # -> 200 OK (no error) ```

3. Check the database: ```sql SELECT model_max_budget FROM "LiteLLM_TeamTable" WHERE team_id='test'; -- -> {…