Temperature coefficient check

Adding a visual check for temperature coefficient reasonableness might be worthwhile. I've found that spec sheet temperature coefficients are not always reliable or available, so something like a scatter plot of filtered normalized energy vs cell temperature could help a user see if their selected value is a good one. See two examples below.

Additional things that might help:

• Using more restrictive filters, just for this step (e.g., increasing minimum POA to ~400 W/m^2)
• Calculating slope of a linear fit to make sure it is close to zero
• Adding an option for calculating temperature coefficient with a regression, skipping user input for this parameter entirely

The issue names no files, tests, or entry points. Start by locating the existing temperature-coefficient analysis and plotting or filtering paths in the Python package, then compare them with the two referenced examples. The scope and completion criteria still need to be decided among visual validation, stricter filtering, slope checking, and regression-based calculation.