Add SociableNumber Implementation

[Rosander0]

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• All new algorithms include a corresponding test class that validates their functionality.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.86%. Comparing base (6fbbc94) to head (5e20539).
⚠️ Report is 5 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7475      +/-   ##
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+ Coverage     79.80%   79.86%   +0.05%     
- Complexity     7302     7338      +36     
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  Files           803      808       +5     
  Lines         23751    23836      +85     
  Branches       4671     4693      +22     
============================================
+ Hits          18955    19036      +81     
- Misses         4036     4037       +1     
- Partials        760      763       +3     

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[Copilot]

Pull request overview

Adds a new number-theory algorithm for detecting whether a given integer belongs to a sociable-number cycle of a specified length, along with JUnit tests validating known sociable/amicable examples and invalid inputs.

Changes:

• Introduce SociableNumber utility with isSociable(number, cycleLength) and a proper-divisor-sum helper.
• Add SociableNumberTest covering a length-5 sociable cycle, amicable pairs (length 2), non-sociable values, and invalid inputs.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
src/main/java/com/thealgorithms/maths/SociableNumber.java	New sociable-number implementation (isSociable) and proper-divisor-sum helper.
src/test/java/com/thealgorithms/maths/SociableNumberTest.java	New unit tests for sociable-cycle detection and edge cases.

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