Add DR restore metadata and backup tasks

[edgard]

Summary

• Add backup, restore, and drill task entry points for the Ansible DR workflow
• Annotate apps with DR tier and restore mode metadata
• Extend metadata validation and inventory generation to enforce DR conventions
• Update restic backup job behavior for safer repository maintenance

Testing

• Updated and expanded unit policy tests for DR metadata rules
• Updated Ansible layout and convention checks to cover the new backup role and playbooks