As a calendar user, I want to set up dates with different highlighted color

As a calendar user, I want to set up dates with different highlighted color and give me an option to do it weekly or monthly ; so that I don't have to set up dates for each week of the month for the rest of the year.

No file, test, or entry point is named. Start by locating the calendar date setup and rendering paths, then clarify how weekly and monthly recurrence should work with different highlight colors. Done means users can configure these schedules and see the expected dates highlighted.

Written by the indexing model from the issue text.