Add Base64Util with encode/decode methods and unit tests

[TonGonzalez]

• 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 code is formatted with clang-format -i --style=file path/to/your/file.java

Description

This PR introduces Base64Util, a utility class for Base64 encoding and decoding of strings.

Key points:

• Added encode(String input) and decode(String base64) methods.
• Implemented comprehensive unit tests in Base64UtilTest covering:
  • Normal strings
  • Empty strings
  • Null input
  • Invalid Base64 input
• Followed the coding and testing conventions of the TheAlgorithms/Java repository.
• Ensures safe and reliable Base64 conversion for various use cases.

If applicable, reference related issue: #<6585>

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.51%. Comparing base (d8ddb07) to head (ca86125).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6593      +/-   ##
============================================
+ Coverage     75.50%   75.51%   +0.01%     
- Complexity     5688     5692       +4     
============================================
  Files           694      695       +1     
  Lines         19570    19579       +9     
  Branches       3791     3791              
============================================
+ Hits          14776    14785       +9     
  Misses         4217     4217              
  Partials        577      577              

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[Arnav-NK]

did you solved the conflict i am getting the same can you help me with that please ?

[TonGonzalez]

Yes, I managed to solve it! I ended up using a website to do the formatting for me, I copied the code and pasted it into the website and then updated my code :) > did you solved the conflict i am getting the same can you help me with that please ?