ci: add basic python workflow

[carlosas]

This PR adds a basic CI workflow using GitHub Actions.
It performs the following checks on every push and PR to main:

• Sets up Python 3.11
• Installs dependencies from requirements.txt
• Runs flake8 to catch syntax errors and undefined names (blocking)
• Runs flake8 for style checks (non-blocking warnings for now)

[Copilot]

Pull request overview

This PR introduces a GitHub Actions CI workflow to automate code quality checks for the Python codebase. The workflow runs on every push and pull request to the main branch, setting up Python 3.11, installing dependencies, and performing two-stage flake8 linting: first blocking on critical syntax errors and undefined names, then running comprehensive style checks as non-blocking warnings.

Changes:

• Added .github/workflows/ci.yml with automated Python code quality checks using flake8
• Configured two-tier linting: blocking checks for syntax errors/undefined names, and warning-only checks for general code quality

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