I use zerotier for that kind of stuff, mostly because it runs native on my router (mikrotik) and is zero config so easy to run on a random mobile device I might have on me.

“If you ever use containers to self-host, do you prefer manual or automatic updates?” “Yes”

That sounds like the kind of stuff we make at $dayjob (that’s for the building trade, where they often have complex spreadsheets and going to an app that calculates everything down to the number of screws for them is a huge benefit).

You could probably still do it with a spreadsheet, just have parts list add/remove fan out into the cutting list and update automatically. I imagine it’d get quite ugly, but doable. If you want to do optimisation (buy 1 5 foot length and cut rather than 2 2 foot lengths, because it’s cheaper, for example) it gets even uglier and at that point a bespoke app becomes more sensible.