Ignore uv.lock

[QuiteYellow]

uv run locks the project directory before it runs anything, so the pinned-interpreter test command writes a uv.lock as a side effect. The file then sat untracked and unignored, one git add -A away from being committed. That happened once already, in the first commit on #98, and had to be amended out.

Nothing in the repo reads it. There is no [tool.uv] in pyproject.toml, and no reference to it in CI or the docs. The dependency strategy argues against keeping one:

	what it pins
pyproject.toml	ranges: cbor2>=5.6, pyOpenSSL>=23.1
CI floor job	exact minimums: cbor2==5.6.0, pyOpenSSL==23.1.0, pytest==8.0.0
CI latest job	unpinned, pip install -e ".[dev]"
a committed uv.lock	one resolution between those two, installed by nothing

Testing the two ends of the supported range is the point of those two jobs. A lockfile pins a point between them that no job installs, so it would drift with nobody watching. It also holds pytest and smartthings-local itself, so what it locks is a dev environment. Consumers get the ranges from pyproject.toml, since only uv reads a uv.lock.

The ignore rule carries that reasoning as a comment, so the next person who wonders why it is ignored can read the answer there.