Feisty first launch 3

Overview. User's registration and first-launch experience must be bug free. Plus XMPP and the Librem 5. Zero-tolerance for UX bugs. They must be fixed in order to close these milestones.

Milestone goal: A registered Librem 5 owner must be able to sign in and use at least one app on their phone. 📯

Replaced by https://source.puri.sm/groups/liberty/-/milestones/26