Add recursive factorial implementation with tests

[koushik-sai]

• Added a recursive implementation of factorial in the recursion package
• Followed utility-class pattern used across the repository
• Included JUnit tests for base cases, positive input, and negative input

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.90%. Comparing base (1eb0d61) to head (267ae5f).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #7178   +/-   ##
=========================================
  Coverage     78.90%   78.90%           
  Complexity     6864     6864           
=========================================
  Files           772      772           
  Lines         22697    22697           
  Branches       4459     4459           
=========================================
  Hits          17908    17908           
  Misses         4073     4073           
  Partials        716      716           

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[DenizAltunkapan]

there already exists a recursive implementation @koushik-sai https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/FactorialRecursion.java .
Would you suggest moving the existing class into the recursive package?
If so, please move it there and remove your implementation.

[koushik-sai]

Thanks for the suggestion 👍
I’ve moved the existing FactorialRecursion from the maths package to the recursion package, removed the duplicate implementation introduced in this PR, updated the corresponding tests, and applied clang-format. All tests pass locally.

[DenizAltunkapan]

Thank you @koushik-sai