Hide notes when app is locked

[F462]

In this PR, the notes are not loaded before the app is unlocked, which one the one hand still preserves the app impression while locked, while at the same time hiding the sensitive data. This solves #927 .

Since I'm quite new to the code, I cannot really judge if this approach is valid. However, it seems to achieve the expected result without side effects (tested on Android 13).

The notes are still shown in the app preview when minimized, which is a separate issue.

In addition, the time based app locking doesn't seem to work on the main screen, which isn't supported by these changes here, either.

[github-actions[bot]]

Hello there, Thank you so much for taking the time and effort to create a pull request to our Nextcloud project.

We hope that the reviewing process is going smooth and is helpful for you. We want to ensure your pull request is reviewed to your satisfaction. If you have a moment, our community management team would very much appreciate your feedback on your experience with this PR reviewing process.

Your feedback is valuable to us as we continuously strive to improve our community developer experience. Please take a moment to complete our short survey by clicking on the following link: https://cloud.nextcloud.com/apps/forms/s/i9Ago4EQRZ7TWxjfmeEpPkf6

Thank you for contributing to Nextcloud and we hope to hear from you soon!

[stefan-niedermann]

Hmm, might work (didn't check it due to missing sparetime at runtime).

However, looking at three different banking apps it seems an dedicated UnlockActicity seems the way to go to solve Googles shit show eventually. 🤷

cc @tobiasKaminsky and @AndyScherzinger for their opinion

[AndyScherzinger]

I agree @stefan-niedermann with the assessment regarding a dedicated activity. This is also how we do it on files and talk.