[FSSDK-12276] update: replace flake8 with ruff

[FarhanAnjum-opti]

Summary

• Replace Flake8 with Ruff as the primary Python linter
• Update lint configuration and CI to use Ruff

The change simplifies the linting setup, improves performance, and reduces dependency overhead while maintaining equivalent linting coverage. Linting errors that do not break code logic can be auto fixed using
ruff check . --fix

Test plan

• Run ruff check . locally
• Run full CI pipeline and verify lint and test steps pass

Issues

FSSDK-12276

[Copilot]

Pull request overview

Replaces Flake8 with Ruff as the project’s Python linter by adding Ruff configuration, updating developer docs, and switching CI to run ruff check.

Changes:

• Add ruff.toml with Flake8-equivalent rule selection (E/W/F) and project excludes.
• Swap Flake8 for Ruff in test requirements and GitHub Actions lint job.
• Update contributor documentation to reference Ruff; remove legacy .flake8.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
ruff.toml	Introduces Ruff config (line length, excludes, selected rule families, per-file ignores).
requirements/test.txt	Replaces flake8 dependency with ruff.
CONTRIBUTING.md	Updates contributor workflow and style notes to use Ruff.
.github/workflows/python.yml	Updates CI lint job to install/run Ruff instead of Flake8.
.flake8	Removes obsolete Flake8 configuration file.

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[Mat001]

LGTM. Make sure that no errors in PR checks.