Implement Apple Music playlist browsing with folders (#3008)

* Implement Apple Music playlist browsing with folders

* Update music_assistant/providers/apple_music/__init__.py

Co-authored-by: Copilot <[email protected]>

* Separate browse logic and handle catalog/library edge cases

* Resolve copilot feedback

* Revert & repair get_playlist

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Co-authored-by: Marvin Schenkel <[email protected]>
Co-authored-by: Copilot <[email protected]>