chore: upgrade litellm to 1.83.7 (#722)

litellm 1.83.7 exact-pins its transitive deps, so this also moves openai 2.28.0->2.30.0 and aiohttp 3.13.3->3.13.5, and pins pydantic 2.12.5, click 8.1.8, jsonschema 4.23.0, importlib-metadata 8.5.0, and python-dotenv 1.0.1 (pydantic-core and typer follow to stay compatible).

Author: mahesh-bespoke