Allow marking a bus as delayed

[alanzhu0]

Feature description

• Allow marking a bus as delayed in the afternoon page.
• It'd be nice if the whole bus admin UI was cleaned up.

Rationale for adding feature

• There should be a way to mark buses as delayed...

Suggested implementation(s) (if applicable)

• Look at the morning bus page (dropdown with buttons to mark as arrived / on time / delayed).
• Most code is there - only the field for status needs a frontend element to allow it to be changed.

[alanzhu0]

Can I get permissions to add labels or can someone add good-first-issue to these four issues (this one, #1413, #1412, and #1411) for me?