[Housekeeping]: Standardize linting on Ruff (remove legacy linters/formatters)

[pheus]

Proposed Changes

• Adopt Ruff as the single linter+formatter (ruff check + ruff format).
• Remove legacy tools and their configs:
  • flake8 (and delete the .flake8 file)
  • black
  • isort
  • pyupgrade
  • add-trailing-comma
  • pylint config (if present)
• Pre-commit:
  • Replace the above hooks with Ruff hooks only:
    • ruff format (autofix on local)
    • ruff check (with --fix locally; --diff/no-fix in CI)
• pyproject.toml:
  • Remove any [tool.black], [tool.isort], [tool.ruff], [tool.pylint] sections so pyproject.toml contains only project/build metadata.
  • Make ruff.toml the single source of truth for Ruff settings.
• Ruff configuration:
  • Copy and adapt the Ruff configuration from the ACI plugin:
    • Source: pheus/netbox-aci-plugin → ruff.toml
      https://github.com/pheus/netbox-aci-plugin/blob/main/ruff.toml
    • Adjust paths/module names for this repo (e.g., src = ["netbox_acls", "tests"], excludes like env/, docs/, etc. as appropriate).
• CI:
  • Update GitHub Actions (and any Makefile targets) to run only Ruff:
    • ruff format --check .
    • ruff check .
  • Remove any steps invoking removed tools.
• Docs:
  • Update CONTRIBUTING.md / README references to mention Ruff + pre-commit and drop mentions of Black/Flake8/Isort/PyUpgrade.
  • Example contributor setup:

    python -m pip install ruff pre-commit
    pre-commit install
    

Justification

• Single, fast toolchain: Ruff replaces the combined roles of Flake8/Isort/PyUpgrade and can format code à la Black, reducing maintenance and speeding up local dev and CI.
• Consistency with other NetBox plugins: Aligns the style with netbox-aci-plugin and simplifies cross-repo contributions.
• Matches current NetBox dev guidance: NetBox docs demonstrate using Ruff + pre-commit as the standard developer workflow.
• Lower config complexity: One ruff.toml at the root avoids conflicting settings spread across multiple tools and pyproject.toml.

Tasks / Checklist

• Delete .flake8.
• Remove black, flake8, isort, pyupgrade, add-trailing-comma hooks from .pre-commit-config.yaml.
• Keep only Ruff hooks:
  • ruff format (local autofix)
  • ruff check (local --fix; CI --diff)
• Remove [tool.black], [tool.isort], [tool.ruff], [tool.pylint] from pyproject.toml (if present).
• Add/align ruff.toml using the config from netbox-aci-plugin, adjusted for netbox_acls.
• Ensure make lint (or equivalent) uses Ruff only.
• Update GitHub Actions to run Ruff only.
• Update contributor docs to Ruff + pre-commit.
• Run repository‑wide ruff format + ruff check --fix and commit style‑only changes.

References

• ACI plugin Ruff config (example to copy):
  https://github.com/pheus/netbox-aci-plugin/blob/main/ruff.toml
• NetBox developer docs (Ruff + pre‑commit in the workflow):
  https://netboxlabs.com/docs/netbox/development/getting-started/
• Ruff configuration reference:
  https://docs.astral.sh/ruff/configuration/