Fix volume mapping for music data in compose.yaml

[jackspiering]

Pull Request Title: Fix volume mapping for music data in compose.yaml

Description

Fix volume mapping for music data in compose.yaml

Related Issues

• Issue Picard setup : error in volumes #194

Type of Change

• Bug fix
• New feature
• Documentation update
• Refactoring

How Has This Been Tested?

Tested on

• OS: Debian GNU/Linux 13 (trixie)
• Architecture: x86_64
• Kernel Version: 6.12.63+deb13-amd64

Docker:

• Server Version: 29.1.4
• API Version: 1.52
• Go Version: go1.25.5

Checklist

• I have performed a self-review of my code
• I have added tests that prove my fix or feature works
• I have updated necessary documentation (e.g. frontpage README.md)
• Any dependent changes have been merged and published in downstream modules

Screenshots (if applicable)

• N/A

Additional Notes

• N/A