Theme per page

### Description

Love using glance!!

I would like to be able to choose a theme for each of my glance pages - I could only see that it could be added to the top level.

for example

Cappuccino Frappe for Home, Teal City for media and so on.

The issue names no files, tests, or entry points. Start by tracing how the top-level theme is configured and applied to pages; done means each page can select its own theme, including the Home and media examples described.

Written by the indexing model from the issue text.