New release: Air v0.9.0

Air is a new private messenger based on the Messaging Layer Security (MLS) protocol. Invite-only for now.

Thank you all for the helpful feedback! This release only contains bug fixes.

🛠️ Fixes:

- Adding a new contact failed if the requester had changed their profile
- Push notifications did not always work on Android
- Uploading attachments could not be tried again
- Buttons could sometimes be pressed too many times
- Contact requests would overwrite existing ones