Replace `/random` with `/search?sortby=rand&browse`

[dfabulich]

The /random page shows random games, but so does /search?sortby=rand&browse, and the search/browse page gets way, way more developer attention.

The one nice thing about /random is that it includes links to other lists, but I think we could put those in a tip box on the search/browse page anyway. #975

[dfabulich]

This would require us to add an operator to filter by starsort: #974

And I guess it would require us to add an operator to filter by cover art…? But, honestly, who cares about that random page… maybe we'd just delete that.