* use freshly designed AppIntro fragments instead of the previous start-up fragments
* About dialog: show translations, updated library view
* use latest version of okhttp (4.5 instead of 3.12); dropping support for API level <21 (Android 5)
* support for Brotli HTTP compression (if supported by server)
* Nextcloud Login Flow: show progress bar and error messages if something goes wrong
* many small bug fixes, improvements, optimizations
