Add geometry algorithm: point in circle check

[keira780]

Implementation of a simple point-in-circle check algorithm in C++. (AI assisted)

This PR adds a C++ implementation to check if a point is within a circle.

1. It includes a reusable function and a main driver for testing.
2. Code is over 10 lines and follows basic C++ standards.
3. Assisted by AI (Trae) for logic optimization.