fix(deps): bump bithuman in uv.lock for Windows wheel support

[abhijeetgaur-dev]

What

Bumps bithuman in uv.lock from 2.11.0 to 2.11.19 via uv lock --upgrade-package bithuman.
bithuman==2.11.19 publishes native win_amd64 wheels on PyPI for Python 3.12, 3.13, and 3.14 alongside macOS and Linux wheels, as well as an sdist fallback.

Why

Running uv sync or uv sync --all-extras --dev on Windows (win_amd64) currently fails out-of-the-box:

error: Distribution `bithuman==2.11.0 @ registry+https://pypi.org/simple` can't be installed because
       it doesn't have a source distribution or wheel for the current platform
hint: You're on Windows (`win_amd64`), but `bithuman` (v2.11.0) only has wheels for the following platforms: `manylinux_2_28_aarch64`, `manylinux_2_28_x86_64`, `macosx_14_0_arm64`

In #7301, bithuman was pinned to 2.11.0 in uv.lock. That release had no Windows wheel or sdist on PyPI, breaking local setup for Windows contributors (as also noted in #7468). Upgrading to 2.11.19 unblocks Windows environments without requiring any code changes.

Verification

• uv sync --dev on Windows (win_amd64): resolves cleanly and installs all workspace members without error.
• ruff check livekit-plugins/livekit-plugins-bithuman: passed.
• ruff format --check livekit-plugins/livekit-plugins-bithuman: passed.
• mypy -p livekit.plugins.bithuman: passed (strict mode, 0 errors in 4 source files).
• Smoke test: uv run python examples/voice_agents/basic_agent.py --help runs cleanly.
• Leaves version.py and plugin manifests unchanged per AGENTS.md versioning rules.

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.