Issue #24: Implement Radix Sort

[Brad-Edwards]

This PR implements the radix sort algorithm with the following features:

• Implementation for non-negative integers (u32)
• O(d * (n + b)) time complexity where d is number of digits and b is base (10)
• O(n + b) auxiliary space
• Stable sorting algorithm
• Uses counting sort as a subroutine for each digit
• Comprehensive documentation
• Extensive unit tests covering:
  • Empty and single-element arrays
  • Already sorted arrays
  • Reverse sorted arrays
  • Random order arrays
  • Arrays with duplicates
  • Large arrays
  • Arrays with all equal elements
  • Numbers with different digit lengths
  • Powers of ten
  • Repeated digits
  • Single digit numbers
  • Stability verification
  • Digit extraction verification
  • Zero and large values

Key advantages:

• Linear time complexity for fixed number of digits
• Stable sorting
• Works well when digit range is small
• Can be faster than comparison-based sorts

Limitations:

• Only works with integers
• Performance depends on number of digits
• Uses extra space proportional to input size