LIMS-2055: Use Compton cutoff energy from the results file

[ndg63276]

JIRA ticket: LIMS-2055

Summary:

Data analysis have suggested adding header rows to .results.dat files, eg

# COMPTON_CUTOFF_EV 9585.53
# COLUMN_HEADERS: Element-Edge Counts Sigma

This means ignoring those lines when it comes to labelling peaks, and reading in the Compton cutoff energy to plot the graph in a different colour.

Changes:

• Swap the order of reading the results.dat file and the .dat file
• Ignore lines starting with '#' for the peak plotting, and still only report the first 5 elements
• Pull out the Compton cutoff energy if given, or use energy - 1100 as a default

To test:

• Go to a visit with MCA spectra, eg /dc/visit/cm44137-1/ty/mca (NB permalinks to individual MCA spectra is broken in 2026-R1.4)
• Open the relevant .results.dat file (found in visit/processed/pymca)
• Add the header from above to the top of the .results.dat file
• Check the light grey line now starts from 9585eV (may look different as the autoscaling is affected)
• Change the COMPTON_CUTOFF_EV to 14900 in the .results.dat file, check the spectra looks like it does on production
• Check a maximum of 5 elements are displayed, though the front end cuts off some of the smaller ones