Qol auto detect surface to volume

[RemDelaporteMathurin]

Description

Needs #1118

Summary

This PR removes the need to explicitly define surface_to_volume when initiliasing a HydrogenTransportProblemDiscontinuous class

Related Issues

Fixes #1117

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 🔨 Code refactoring (no functional changes, no API changes)
• 📝 Documentation update
• ✅ Test update (adding missing tests or correcting existing tests)
• 🔧 Build/CI configuration change

Testing

• All existing tests pass locally (pytest)
• I have added new tests that prove my fix is effective or that my feature works

Code Quality Checklist

• My code follows the code style of this project (Ruff formatted: ruff format .)
• My code passes linting checks (ruff check .)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas

Documentation

• I have updated the documentation accordingly (if applicable)
• I have added docstrings to new functions/classes following the project conventions

Breaking Changes

Screenshots/Examples

Additional Notes

[codecov]

Codecov Report

❌ Patch coverage is 95.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.91%. Comparing base (3c3532e) to head (a6306eb).

Files with missing lines	Patch %	Lines
src/festim/hydrogen_transport_problem.py	80.00%	1 Missing ⚠️
src/festim/subdomain/volume_subdomain.py	96.87%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1122      +/-   ##
==========================================
- Coverage   94.92%   94.91%   -0.01%     
==========================================
  Files          44       44              
  Lines        3268     3304      +36     
==========================================
+ Hits         3102     3136      +34     
- Misses        166      168       +2     

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