optional shared y-axis for matching sensor units

[nicevibesplus]

Description

Add a button to let users merge matching chart y-axes into one single y-axis. When a graph has two or more sensors that use the exact same unit (like °C), users can click an option to combine them into one y-axis.

As the legend already explains the type of measurement, the current title of the y-axis is redundant information and could be shortened to just the unit. This also removes the current limit of only showing 2 sensors at a time.

Use case

• show more than 2 sensors, even more important if comparison of multiple devices is back.
• fix confusing visuals, since right now 15°C and 5°C may overlap
• clean up the screen by hiding redundant information in the graph

Implementation ideas (optional)

No response

Additional information (optional)

No response

[jona159]

Good idea to have a shared y-axis!
If you take a look at the feat/device-sensor-comparison i already worked a bit on this (in Graph.tsx starting from line 180), but it currently only shares the axis if title and unit match. You are right that for a comparison it should be enough for the unit to match in most cases, my only concern would be completely unrelated sensors that measure in the same unit (for example in our sensor-definitions we have a couple of sensors that measure in percent, like soil moisture and relative humidity) where i dont know if this could be visually confusing to look at if they share the same axis. Although this might not be a problem if we assume the user intentially picks comparable sensors.