Complete Activities.tsx Page

back needs to be a scrollview of all of a users activities. For now can just list them but eventually need to be able to go back and change things about them, delete them, etc.

Start with Activities.tsx and inspect how the page currently renders and obtains user activities. Make the page show the user's activities in a scrollable list, with listing the activities as the done condition; editing and deletion are explicitly future work.

Written by the indexing model from the issue text.