New storage selector, other minor improvements

This release adds a new storage selector and other minor improvements. This new selector can pick the app's external storage directories, which should get around Android permission issues.

Changes

• New storage selector.
• Add long press on log tile to copy log.
• Added warning for when a custom storage path returns "/" (also changed the text style of that widget).
• The base URL will now be trimmed when logging in, so whitespace at the end shouldn't cause an error.
• Logs should now be properly reversed.
• The logging system now catches Flutter errors. This means that whenever something goes wrong in the UI, the error should show up in the logs. This also includes a stacktrace. Many other errors that were previously not logged should now be logged.
• Added an option to disable audio service low-priority on pause. This option is enabled by default, and allows for the app notification to be swiped away when paused. This also allows Android to kill the service to free resources, which could mean that the audio service is closed when you don't want it to. Disabling this option should keep the audio service running until you manually stop it.