Make the bars have colors on the repos page

Tucker McKnight <tmcknight@instructure.com> | Wed Jul 22 2026

Make the bars have colors on the repos page

Adds a new, optional parameter to the repo configuration:
defaultTemplateConfiguration.colors.languageGraph. This should be
an array of hex color strings (or anything else that can be used as
a `background-color: <here>;` value in CSS).

Also includes some style and spacing tweaks for the new header,
especially at small widths.