[SandObserver]

Summary

• When a Proxmox Backup Server group is missing from its saved namespace, search the datastore's other namespaces for the same type and id, and follow it only on exactly one match.
• Remember the new namespace per card in memory, bounded, so the search runs once. Saved settings are not changed.
• Read the card's tasks against the namespace the group is in now.
• Keep the original error when the saved namespace cannot be listed and no single match is found.

Testing
All green. Added tests for a moved group, a moved namespace, a group moved back, two matches and a removed group.

Changelog

Checklist

• Stays within the project constraints: one container, no runtime dependencies, no build step (see CONTRIBUTING.md).
• Tests added or updated for new logic, and the full suite, lint, and typechecks pass.
• Docs updated if behavior or configuration changed.