feat(strings): add MoveHashToEnd algorithm

[ShyamChavda005]

• Add MoveHashToEnd utility class that moves all '#' characters to the end of a string while preserving the order of other characters
• Algorithm runs in O(n) time and O(n) space using a two-pass approach: first collects non-'#' chars, then fills remaining positions with '#'
• Add null and empty string guards
• Add MoveHashToEndTest with 9 unit tests covering normal, edge, and boundary cases (null, empty, all-hash, no-hash, single char)

• 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 79.45%. Comparing base (5e06b15) to head (a4e248a).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #7313   +/-   ##
=========================================
  Coverage     79.44%   79.45%           
- Complexity     7064     7069    +5     
=========================================
  Files           788      789    +1     
  Lines         23129    23139   +10     
  Branches       4548     4551    +3     
=========================================
+ Hits          18375    18385   +10     
  Misses         4022     4022           
  Partials        732      732           

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