Visualization: unknown power

[naltatis]

fixes #16148

Introduce a question-mark when input and output don't match up.

• ⬇️ imported power to low: show a question mark bracket at the top
• ⬆️ imported power to high: show a question mark bracket ad the bottom and add a gray box to the color segments in the middle.
• 🚧 only show unknown areas if mismatch between in and out is above 10% to avoid flickering during normal operation due to meter reading delays.

For later:
Maybe add a label that explains the question mark and gray box.

[StefanSchoof]

The case "imported power to low:" is also the case, charger has no meter and car is taking less as by evcc allowed. I am unsure if adding here a question mark to the production will make this case worse.