chore: tidy up and refactoring

[PeterBaker0]

Removes all methods I could identify as being completely unused/deprecated. I.e.

• all previous job management system
• all previous job routes
• all previous regional/suitability API routes

Also removes a bunch of multiple dispatched wrappers of some of the assessment methods that were unused.

Moves a bunch of files around to try and make code structure a bit clearer, i.e.

• applies a barrel import approach similar to TS, top level imports index.jl files, then index.jl files include that modules files
• moves the modules dependencies into the index.jl file, since they were often stealthily shared between the files within a module anyway (making them sensitive to the order in which includes were executed)
• tries to rename files/restructure to remove duplication, and make files have a single purpose where possible

NOTE: some methods I deleted we may want to retain (possibly for exposing some testing functionality/use cases I wasn't aware of). I've gone for the 'if unsure, delete' approach - but we can selectively bring stuff back if there is a good reason for it being there.

[ConnectedSystems]

Minor comments to maintain Julia conventions.

Thanks for cleaning out the cruft!