Auto-archive: prerequisite work

[johnswanson]

Tasks

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1. Add a last_viewed_at timestamp to dashboards #44251
   +0
2. Don't sort official collections first in the trash #44373
   +0

Some motivation:
Official collections are always sorted first in the collection view. This means they are here always first since we're reusing that. And if you have 25 or more, they dominate the first page and it seems like the sorting doesn't work.

For "last_edited_at" for collections, probably the principal way you would sort this list is by recency. And since we don't have this information for collections, if you trash a collection you cannot find it by "last edited at" or "trashed at" (as we show last edit at in the trash). Backfilling this makes collections findable.