Allow pytest-asyncio 1.4

[abrookins]

Supersedes #837. Updates the development requirement and the corresponding uv.lock metadata.

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Note

Low Risk
Dev-only dependency constraint and lockfile metadata; no runtime or application code changes.

Overview
Widens the dev dependency cap for pytest-asyncio from <1.4 to <1.5, so installs can resolve 1.4.x while staying below 1.5. uv.lock is updated to match the new specifier.

Also removes a stray blank line under [tool.mypy] in pyproject.toml (formatting only).

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