* ui: types and stubs to encrypt local files
* ios: encrypt automatically received images in local storage
* encrypt sent images, marked to be received via NSE
* ios: encrypt sent and received local voice files
* encrypt sent and received local files
* fix NSE
* remove comment
* decrypt files in background thread
* light github image for dark mode
* show message received status, remove chevrons in chat list
* show unread message status
* add message send error mark
* refactor alerts to use AlertManager
* show alert message on tapping undelivered message, simplify text-only alerts