Residue offset in web application

To account for purification tags, sometimes the residue number needs to be offset

This would require adding a 'residue_offset' field to PeptideInput controller; as well as the .yaml HDX measurement spec files.

Locate the PeptideInput controller and the .yaml HDX measurement spec files mentioned in the issue. Trace how residue numbers are read and used, then verify that a residue_offset field is accepted in both places and that residue numbering reflects the offset.

Vom Indexierungsmodell aus dem Issue-Text verfasst.