fix: add mock data and cache to theme service

[mrv777]

Description

• The current theme service doesn't work well in localhost testing since it can't pull the info from the device, so this adds mock data
• getThemeSettings is called a few times on load so adding a cache should just do one API call instead of the 5+ we currently do. Just did 1 second to start to keep the data fresh while preventing all these same calls in the same second

[WantClue]

LGTM, but do we actually need to load in mock data?

[mrv777]

LGTM, but do we actually need to load in mock data?

I could be doing it wrong, but without the mock data when I try to just run the UI locally for testing no theme gets loaded so a lot more is black then there should be and doesn't look right

[eandersson]

LGTM, but do we actually need to load in mock data?

I could be doing it wrong, but without the mock data when I try to just run the UI locally for testing no theme gets loaded so a lot more is black then there should be and doesn't look right

I haven't tried it in a while with themes, but I believe we do need it for local testing.