✨ add department filter

[ctcpip]

note: this is built on top of the changes from #58. the new changes can be viewed in isolation here.

this feature does the following:

• loads the currently available departments
  • the departments are cached, and only fetched again after a week or more. (department options virtually never change)
• renders the options for the user, allowing them to choose
• stores their choices locally and busts the artwork cache so their preferences take effect immediately
• choices are used to filter the query used to fetch artworks

additional considerations:

• we add a none option because there are many artworks that do not have an assigned department
• there is a contemporary art department, but we get zero results if we filter on it for some strange reason. as such, we exclude this option
• this also includes some refactoring to share code between the options page and the art tab page, code organization, and layout updates in the options page

resolves #52 and further resolves #19