feat: implement Sudoku Solver with full coverage and fixed legacy Jav…

[subhammohanty-sys]

Changes :-

• Sudoku Solver - Implemented a backtracking-based solver with pre-validation logic.
• Legacy Fix - Fixed Dangling Javadoc warnings in some files which caused build failures under strict -Werror settings.
• Testing - Achieved full test coverage using JUnit 5.
  Closes [FEATURE REQUEST] Add Sudoku Solver using Backtracking #6929

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

[codecov-commenter]

Codecov Report

❌ Patch coverage is 94.28571% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.56%. Comparing base (e814d97) to head (767f6c5).

Files with missing lines	Patch %	Lines
...a/com/thealgorithms/backtracking/SudokuSolver.java	97.05%	0 Missing and 1 partial ⚠️
...om/thealgorithms/conversions/AnyBaseToAnyBase.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7422      +/-   ##
============================================
+ Coverage     79.53%   79.56%   +0.02%     
+ Complexity     7177     7174       -3     
============================================
  Files           798      798              
  Lines         23474    23470       -4     
  Branches       4617     4617              
============================================
+ Hits          18671    18674       +3     
+ Misses         4055     4046       -9     
- Partials        748      750       +2     

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