Added one time pad cipher

[Shewale41]

Added One-Time Pad Cipher Implementation

This pull request adds an implementation of the One-Time Pad Cipher under the ciphers package.
The One-Time Pad Cipher is a symmetric encryption technique that XORs plaintext with a random key of equal length, providing perfect secrecy when the key is truly random and used only once.

Features:

• Uses SecureRandom for key generation.
• Provides methods for both encryption and decryption using XOR.
• Includes JavaDoc with reference to the official algorithm documentation.

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 include a reference link in their comments.
All code is formatted with clang-format -i --style=file path/to/your/file.java.

File Added:
src/main/java/com/thealgorithms/ciphers/OneTimePadCipher.java

---

Fixes issue: #6941

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.19%. Comparing base (21eff8a) to head (1e78a3f).

Files with missing lines	Patch %	Lines
...va/com/thealgorithms/ciphers/OneTimePadCipher.java	0.00%	22 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6966      +/-   ##
============================================
- Coverage     78.26%   78.19%   -0.08%     
  Complexity     6573     6573              
============================================
  Files           743      744       +1     
  Lines         21895    21917      +22     
  Branches       4288     4290       +2     
============================================
  Hits          17137    17137              
- Misses         4074     4096      +22     
  Partials        684      684              

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[github-actions]

This pull request has been automatically closed because its workflows or checks failed and it has been inactive for more than 14 days. Please fix the workflows and reopen if you'd like to continue. Merging from main/master alone does not count as activity.