feat: Add Ruff linting workflow and fix code quality issues

[neverbiasu]

Summary

Added automated Python linting with Ruff and fixed existing code quality issues across the codebase.

Changes

• Added GitHub Actions workflow for Ruff linting
• Fixed 25+ linting issues (imports, unused variables, formatting, etc.)
• Excluded problem.py files (educational templates)
• All existing functionality preserved

Benefits

• Consistent code style
• Automated quality checks for future PRs
• Better maintainability

Files modified: 10+ solution files across various problems

Workflow Results

1. Ruff detected code quality issues and action failed.
   

2. Action successed.
   

[neverbiasu]

@moe18 please review my PR, any suggestions are appreciated.

[moe18]

@neverbiasu thank you for the work you put into this, would you be able to make it work with the new structure of the repo, if not I will work on it

[neverbiasu]

@moe18 no problem, I'll work on it

[neverbiasu]

@moe18 I've revised, please check if its meet your requires.