Abstract local config's into KlipperLCD.cfg to avoid 'dirty' update message

[jcfield-boop]

I might have a go at this with Claude Code - but it's annoying!

You have to change the user and paths in the KlipperLCD.service and main.py to match your local config which makes the ability to include in the 'Machine' update service trigger a "Repo is dirty" message as it's the same version but has parameters changed in these files.

[jcfield-boop]

I did a fork and have done the abstraction https://github.com/jcfield-boop/klipperlcd.git

[jcfield-boop]

I'm still waiting for a new motherboard to check it's working but my buddy Claude thinks it is...