A: This depends on the platform of your mobile device. For iPhones, Sensei Project Online Time Reporter uses Keychain to store user credentials on the device. iOS provides a keychain to all iOS apps that can be used to store all sorts of sensitive data. More information on Keychain can be found here: https://support.apple.com/en-us/HT204085
For Android devices the Sensei Project Online Time Reporter leverages Android Keystore. This allows the app to store cryptographic keys in a container to protect the credentials from unauthorized use. More information can be found here: https://developer.android.com/training/articles/keystore
Both the above methods prevent the extraction of the user credentials from the device. If the app is removed from the device all data (including credentials) is removed as well.