test: pytest suite + ruff/mypy + CI

[solomonneas]

Adds the test and CI harness the repo was missing. The CLI does bulk destructive operations (block/forget by regex) and previously had zero tests, no linter, and no CI.

What's added

• 94 unit tests (tests/) over the pure sync logic, no network:
  • response-shape extraction (_extract_data_list, _extract_networks, id parsing)
  • device/profile match resolution, including the ambiguous-query refusal that stops a destructive command acting on the wrong device
  • _filter_devices paths, day/time validation, _fmt_last_active buckets
  • the argparse command surface (every subcommand resolves; required args enforced)
• [dev] extra (pytest/ruff/mypy) + ruff/mypy/pytest config in pyproject.toml
• GitHub Actions CI (.github/workflows/ci.yml) running lint + types + tests on push/PR
• Fixed the pre-existing lint/type findings the new tooling surfaced (all behavior-preserving: timezone.utc->UTC, raise ... from, contextlib.suppress, two mypy narrows, wrapped long help strings)

Verification

ruff check .   -> All checks passed!
mypy           -> Success: no issues found in 3 source files
pytest         -> 94 passed

Test fixtures use RFC 5737 documentation IPs (no real network addresses).