AccountsScreen: move navigation drawer to foreground so that it overlays FABs when open

[ArnyminerZ]

The PR should be in Draft state during development. As soon as it's finished, it should be marked as Ready for review and a reviewer should be chosen.

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Purpose

Solves #763 by switching the order of the Composables, which places the FABs correctly, below the side drawer.

Short description

Moved Scaffold inside of ModalNavigationDrawer instead of the other way around.

See:

Checklist

• [x] The PR has a proper title, description and label.
• [x] I have self-reviewed the PR.
• [x] I have added documentation to complex functions and functions that can be used by other modules.
• [x] I have added reasonable tests or consciously decided to not add tests.