Post-game details cleanup

[sei-bstein]

Currently, players are able to return to gameboards after the game has ended. We purposefully allow this because players still need to be able to review their challenge scores, view the overall scoreboard, and fill out challenge feedback when a game has ended.

However, this process needs a little cleanup. Currently, players can click on old challenges, and when they do, they get an "inactive session" error.

The ideal solution would be to create a new screen dedicated to encapsulating everything players can do with a game and its challenges once the game ends, which are:

• view the scoreboard
• give challenge feedback
• easily access to their own performance on the challenges

We'd then redirect players to this screen when time runs out or if they're accessing the game after their session (or the execution period) has ended.

[sei-bstein]

This is also a good place for the upcoming feature described in #110.

[sei-bstein]

As part of this item, address the issue where games that have been transitioned to practice mode don't appear in the "previous games" list of the landing page. Link these to the new postgame details screen described in this issue.