PLTF-3363: Upgrade LiteLLM to 1.93.0

[aivong-openhands]

Summary

• Pins litellm to 1.93.0 (was 1.84.1).
• Regenerates uv.lock.

1.93.0 carries the upstream CacheCodec fix
(BerriAI/litellm#27874):
serialization dropped user_id when None while deserialization still required
it, so every Redis cache read of a team-scoped key raised a pydantic validation
error.

No other pins move. 1.84.1 and 1.93.0 declare identical core constraints
(openai<3.0.0,>=2.20.0, aiohttp<4.0,>=3.10, pydantic<3.0.0,>=2.10.0,
httpx<1.0,>=0.28.0), and the vendored SDK asks for litellm>=1.84.1, so
==1.93.0 satisfies it as-is.

Note on lock file scope

Regenerating dropped three greenlet 3.2.4 s390x wheel URLs. Those entries are
pre-existing and unrelated to this change — the wheels are still on PyPI, current
uv just no longer records wheels outside the project's resolution environments.
Everything else in the lock diff is litellm.

Validation

• Parsed modified pyproject.toml with Python tomllib; confirmed the pin reads litellm==1.93.0.
• Ran uv lock — resolved 426 packages, single change reported: Updated litellm v1.84.1 -> v1.93.0.
• Ran uv lock --check — clean.

This PR was drafted by an AI agent on behalf of the user.