Replace the hardcoded /volume1 path with a matrix_base_synology_volume_path
variable (defaulting to /volume1), used both by the setup-time prerequisites
task and by the boot-fix recovery script. This keeps the path consistent with
the rest of the configuration and lets users on a non-default Docker storage
volume override it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>