[Feature]: Use color from entity registry

[Misiu]

Requirements

• I've checked that I'm using the latest version of Calendar Card Pro
• I've verified this feature isn't already available in the configuration options
• I've searched existing issues to verify this hasn't already been requested

Is your feature request related to a problem?

My recent change is adding initial color to calendar entities - home-assistant/core#145606.
I've also added suppoer for Google Calendar entities to import color when firstly imported to HA - home-assistant/core#161671

On the frontend side, users will be able to change that initial color to the color they want - home-assistant/frontend#28882

I think the color should be picked from the entity registry, so we have the same color in all the places

Describe the solution you'd like

The component is able to pick a color from the entity registry

Describe alternatives you've considered

No response

Example use case

I have "trash day" calendars, each with a specific color. I want to see those colors in the card.

Additional context

No response

[navanod-git]

+1 for this, some of our calendars are work related others are general family, would be great to be able to highlight the events related to the work calendars.

[LiquidPT]

This. I just realized you can set colors on calendar entities now. This is a much more central place to set desired colors so that it displays with the same colors in multiple places.