Allow setting min/max graph temp to something else than 0/99°C

[zopieux]

Is your feature request related to a problem? Please describe.

I can't see small changes in temperature because the temp graph scale is hardcoded to whatever sensors tell is the max temperature, and then max(this, 99), similarly for the min. This is not useful. Computers usually operate best within fairly small ranges of temperatures, not "disk specs" or "0-99".

Describe the solution you'd like

I'd like overrides in the "Graph" menu to set the minimum and maximum for the temperature scale, so the live graphs become useful & meaningful, not just all flat-ish.

Additional context