Notification crash and safety improvements
- Don't ever call Q_UNREACHABLE (due to the unknown nature of what we're receiving.) Other clients use a generic "New notification received" in this case, and that's good enough here too.
- Improve the notification text, by explicitly saying it's intentionally blank. Also add the user bio into the relevant notifications.
- Make sure to check if the account is limited before gleefully showing their profile from Tokodon. Hopefully this hasn't happened yet, but that could be an issue sometimes.