Implement Bidirectional BFS algorithm

[darkatwi]

This class implements the Bidirectional Breadth-First Search (BFS) algorithm to determine if a path exists between two nodes in an unweighted graph. It explores the graph from both the start and goal nodes simultaneously, improving efficiency for large graphs.

• 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.
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[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 28 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.47%. Comparing base (a9ba87c) to head (bc05bce).

Files with missing lines	Patch %	Lines
...rithms/datastructures/graphs/BidirectionalBFS.java	0.00%	28 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7146      +/-   ##
============================================
- Coverage     78.56%   78.47%   -0.10%     
- Complexity     6794     6795       +1     
============================================
  Files           762      763       +1     
  Lines         22520    22548      +28     
  Branches       4429     4436       +7     
============================================
+ Hits          17693    17694       +1     
- Misses         4115     4143      +28     
+ Partials        712      711       -1     

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