⚡ Bolt: Refactor iterrows to itertuples/to_dict for performance

[alinelena]

💡 What: Refactored .iterrows() in four files (calc_elasticity.py, gscdb138.py, calc_solvMPCONF196.py, calc_MPCONF196.py) to use .itertuples(index=False) or .to_dict("records").

🎯 Why: iterrows() is a significant performance bottleneck due to the overhead of instantiating a Series object for each row. Using itertuples() provides standard tuple iteration which is substantially faster.

📊 Impact: Expected to significantly reduce the time spent iterating over datasets in DataFrame structures within calculation logic, specifically improving calculation setup performance.

🔬 Measurement: I ran tests to verify the accuracy of the updated indexes, ran formatting and linting, and confirmed via uv run python -m py_compile that the logic matches syntactically without errors. Also noted the learning in .jules/bolt.md.

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PR created automatically by Jules for task 14177908089133039492 started by @alinelena

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