Increase timeouts for sprints

This morning, our Chippy session for our sprint disappeared within an hour of finishing allocation. We were still in the process of planning and realized that Labor Day is in this sprint, so we wanted to go back and change some allocations. However, the sprint could no longer be found -- refreshing the page kicked us back to the "Create new sprint" dialog.

Timeouts should be increased so that the allocation can be returned to during a sprint planning meeting.

Start by reproducing the sprint allocation flow described in the issue and locate where the session or sprint timeout is set. The work is done when an allocated sprint remains available for revision throughout a planning meeting, with a regression check for the reported expiration behavior.

Written by the indexing model from the issue text.