feat: Add .venv to .gitignore and improve script error handling

[slavb18]

Adds the .venv directory to the .gitignore file to prevent accidental commits.

Also, enhances the scripts/setup-python.sh script to include error handling for the pip install command, providing a more informative message if the upgrade fails.

Description

Brief description of the changes in this PR.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)

Related Issues

Fixes #153

Changes Made

• Added error message when pip command fails
• Added .venv to gitignore (common path for venv)

Testing

Describe the tests you ran to verify your changes:

• Unit tests pass (cd core && pytest tests/)
• Lint passes (cd core && ruff check .)
• Manual testing performed

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Screenshots (if applicable)

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