feat: add duplicate_file_finder utility script and update README

[Spirit019]

Description

Please include a summary of the changes and related context. Explain the problem you're solving or feature you're adding.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Code cleanup/refactoring

Related Issues

Closes #(issue number)

Testing

Please describe the tests you've run to verify your changes:

• Manual testing
• Added automated tests
• Existing tests pass

Checklist

• My code follows the project's code style
• I have commented my code, particularly in hard-to-understand areas
• I have updated the README.md if needed
• My changes generate no new warnings
• I have tested my code locally
• New and existing tests pass with my changes

Screenshots (if applicable)

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