### Check for existing issues

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

### The Feature

Add the following read-only endpoints to `admin_viewer_routes` in `litellm/proxy/_types.py` so the `proxy_admin_viewer` role can call them:

- `/spend/logs` - `/spend/logs/ui` - `/spend/logs/v2` - `/spend/logs/session/ui` - `/spend/logs/ui/{request_id}`

All are pure GET / read endpoints.

### Motivation, pitch

The official LiteLLM RBAC table describes `proxy_admin_viewer` as:

> Can login, view all keys, **view all spend across the platform**. > Cannot create keys/delete keys/add new users.

But in practice `proxy_admin_viewer` gets `403 Forbidden` on `/spend/logs/ui`

### What part of LiteLLM is this about?

Proxy

### LiteLLM is hiring a founding backend engineer, are you interested in joining us and shipping to all our users?

No

### Twitter / LinkedIn details

https://www.linkedin.com/in/세환-김-a31543202/