[marvinctl]

What changed and why

• Read scheduled repositories from the Actions variable AUTO_MERGE_REPOS, using comma-separated full names. Reject blank, malformed, unknown or duplicate entries before processing any PRs.
• Keep manual selection, the release switch, fortnightly timing, author filter and merge behavior unchanged. Validation reuses the existing app list.

Set the repository Actions variable before the next scheduled run. To keep the existing selection:

FossifyOrg/Calendar,FossifyOrg/Documents,FossifyOrg/File-Manager,FossifyOrg/Gallery,FossifyOrg/Messages,FossifyOrg/Thank-You,FossifyOrg/Voice-Recorder

Tests performed

YAML parsing, Bash syntax, 60 offline selection checks, and diff whitespace checks passed. No live merge run was used.

Checklist

• Infrastructure / tooling change
• Self-reviewed the changes
• Understand every change in this pull request