Add Dijkstra Algorithm Implementation Using PriorityQueue (Fixes #7112)

[prasanth-30011]

Summary

This Pull Request adds a clean and efficient implementation of Dijkstra’s Algorithm using a PriorityQueue, as requested in issue #7112.

What This PR Includes

• New file Dijkstra.java inside the appropriate package.
• Implementation of Dijkstra’s shortest-path algorithm using:
  • Adjacency list representation
  • Min-heap (PriorityQueue)
• Detection and handling of negative weighted edges (throws exception, as required).
• Code follows the structure, style, and formatting used throughout the TheAlgorithms/Java repository.

Why This Change Is Needed

The project did not previously include a fully correct and optimized Dijkstra implementation using a PriorityQueue.
This PR fills that gap and matches the algorithm request posted under issue #7112.

Related Issue

Fixes #7112

[codecov-commenter]

Codecov Report

:x: Patch coverage is 96.49123% with 2 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 78.55%. Comparing base (e6c576c) to head (02f4f23). :warning: Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
...com/thealgorithms/greedyalgorithms/KruskalMST.java	95.45%	1 Missing and 1 partial :warning:

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7123      +/-   ##
============================================
+ Coverage     78.46%   78.55%   +0.08%     
- Complexity     6746     6748       +2     
============================================
  Files           758      760       +2     
  Lines         22339    22431      +92     
  Branches       4384     4405      +21     
============================================
+ Hits          17528    17620      +92     
+ Misses         4107     4102       -5     
- Partials        704      709       +5     

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