Get the app on the Play Store

My ultimate goal for the app is to offer it publicly on the Play Store. (it would also solve the mess we had of putting apk files on discord, etc).

We'll need to do a bit of work to get the app into a state where it can be used by multiple teams without interfering with each other's data. Off the top of my head:

- [ ] redesign the database server so that multiple teams can upload data, and they don't see each other's data.

Start by reviewing the app's current database-server arrangement and the Play Store goal described in the issue. Define how multiple teams will upload data without seeing one another's data, then identify the affected Android and server entry points. Done means the requirements and implementation scope for team isolation are clear and the app can support the intended multi-team use.

Written by the indexing model from the issue text.