Fix binary search duplicates 13886

[rachit-27]

Summary

Fixes incorrect output of the binary_search() function when duplicate elements exist.

Details

• Updated binary_search() in searches/binary_search.py to correctly return a valid index even when duplicates are present.
• Added tests in tests/searches/test_binary_search_duplicates.py to validate behavior for duplicates, unique elements, and not-found cases.
• Verified style compliance using Ruff and pre-commit.

Issue Reference

Fixes #13886

[algorithms-keeper]

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