ci(workflows): add ci workflow with linting and unit testing

[yxlao]

Summary

• Add GitHub Actions CI for linting and unit tests.
• Match the CamTools trigger convention: manual dispatch, pushes to main, and PR opened/reopened/synchronize events.
• Run pre-commit once on Ubuntu/Python 3.10, test all supported Python versions on Ubuntu, and add a macOS Python 3.13 smoke lane for the primary user platform.
• Use locked uv installs, uv cache, minimal contents: read permissions, concurrency cancellation, and Node 24-backed action versions.

Verification

• uv run pre-commit run --all-files
• uv run python -m unittest discover -s tests -v
• GitHub Actions PR ci(workflows): add ci workflow with linting and unit testing #18: lint and all unit-test jobs passed.