Add palindrome number checker

[amank-23]

This PR adds a palindrome number checker to the math folder.

The implementation checks whether an integer reads the same forward and backward by reversing the number and comparing it with the original.
Self-tests using assert() are included to validate correctness.

Checklist

Added description of change

File name follows the guidelines (palindrome_number.cpp)

Added tests and all tests pass

Added Doxygen-style documentation

Relevant documentation/comments included

PR title follows commit/semantic guidelines

No duplicate implementation exists

I acknowledge that all my contributions will be made under the project's license

Notes

The implementation follows the format, documentation standards, and testing style used across the existing mathematical algorithms in this repository.

[github-actions]

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