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

❌ Patch coverage is 71.42857% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.88%. Comparing base (48e02b3) to head (6bbabd8).

Files with missing lines	Patch %	Lines
...om/thealgorithms/recursion/FactorialRecursion.java	71.42%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7178      +/-   ##
============================================
- Coverage     78.90%   78.88%   -0.02%     
- Complexity     6858     6860       +2     
============================================
  Files           771      772       +1     
  Lines         22688    22695       +7     
  Branches       4457     4458       +1     
============================================
+ Hits          17901    17902       +1     
- Misses         4072     4076       +4     
- Partials        715      717       +2     

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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.