refactor: improve Floor method to handle edge cases

[vardhan30016]

• Add edge case handling for NaN, Infinity, and out-of-bounds values
• Improve consistency with Ceil.java implementation
• Add handling for positive numbers between 0 and 1
• Update Javadoc to match Ceil.java format and clarity
• Use long cast to handle larger numbers correctly

• 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

[codecov-commenter]

Codecov Report

❌ Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 78.51%. Comparing base (a14e1e3) to head (57a165b).

Files with missing lines	Patch %	Lines
src/main/java/com/thealgorithms/maths/Floor.java	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7138      +/-   ##
============================================
- Coverage     78.51%   78.51%   -0.01%     
- Complexity     6752     6755       +3     
============================================
  Files           759      759              
  Lines         22402    22405       +3     
  Branches       4400     4401       +1     
============================================
+ Hits          17589    17591       +2     
  Misses         4108     4108              
- Partials        705      706       +1     

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