Show recently added cards

[Taum]

As a user, I want to see what new cards appeared on the marketplace, so that I don't have to go over cards that I have likely already seen.

Do either or both of these:

• Create a page that lists the cards added during the last market index
• Add an option to /search where only the cards added during the last market index are shown

The database structure has a concept of generation that increments on every market batch indexing. We can rely on this to only show cards with a lastSeen generation greater than or equal to the last completed generation.