Handle short form hex colors in conversion functions

[karwosts]

Proposed change

Some themes use short form hex codes like #F00, but our color converters don't understand this for things like graph colors and energy dashboard.

We can handle this by converting to long form in the theme conversion function.

Also update to strip alpha codes from hex colors, in case some people accidentally use them (similar to how we already ignore for rgba()). The only use of this function is currently in graph cards where alpha channel is always manually manipulated, so we don't want it. If some other use comes up in the future, we could modify the function with an optional parameter to keep or toss the alpha.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

Additional information

• This PR fixes or closes issue: fixes Energy: Wrong color in device chart #24592
• This PR is related to issue or discussion:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io