[FEAT] Add Thin Lens formula for ray optics

[koushik-sai]

Description

This pull request adds an implementation of the Thin Lens formula used in ray optics.

The class provides:

• Image distance calculation using the thin lens equation
• Magnification calculation
• Real vs virtual image determination

Notes

• Uses Cartesian sign convention
• Includes input validation for physical correctness

Reference

• https://en.wikipedia.org/wiki/Thin_lens

[codecov-commenter]

Codecov Report

❌ Patch coverage is 22.22222% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.89%. Comparing base (b76962d) to head (c5e35a6).

Files with missing lines	Patch %	Lines
.../main/java/com/thealgorithms/physics/ThinLens.java	22.22%	5 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7170      +/-   ##
============================================
- Coverage     78.91%   78.89%   -0.03%     
- Complexity     6853     6856       +3     
============================================
  Files           769      770       +1     
  Lines         22668    22677       +9     
  Branches       4456     4456              
============================================
+ Hits          17888    17890       +2     
- Misses         4067     4072       +5     
- Partials        713      715       +2     

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[koushik-sai]

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