Use PQAnalysis for gen parsing

[galjos]

Summary

• Delegate .gen parsing to PQAnalysis.io.read_gen_file.
• Preserve ThermoScreening's existing read_gen() return format.
• Add PQAnalysis 1.3.0+ as a runtime dependency and align CI with Python 3.12.

Validation

• python -m pytest tests/thermo/test_api.py -q
• isolated install of PQAnalysis==1.3.0 reads geo_opt.gen
• python -m pip install --dry-run .
• python -m pytest --cov=ThermoScreening --cov-report=term-missing -q

Refs #10

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.58%. Comparing base (d90b781) to head (f194beb).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #27      +/-   ##
==========================================
+ Coverage   87.01%   88.58%   +1.56%     
==========================================
  Files          20       20              
  Lines        1063     1060       -3     
==========================================
+ Hits          925      939      +14     
+ Misses        138      121      -17     

Flag	Coverage Δ
unittests	88.58% <100.00%> (+1.56%)	⬆️

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