Operator: Shuffle-all belongs in the Library view, not the Home
app bar. Moved the shuffle IconButton to LibraryScreen's app bar
(same behavior — online server-random / offline cache-union via
shuffleSourceProvider); reverted Home's app bar to the original
MainAppBarActions-only and dropped the now-unused imports.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>