feat: add cluster group failover mode and fix tasks focus freeze

[al-bashkir]

Introduce per-group mode settings and cluster-aware UI/client switching so same-cluster profiles can run with active node failover from the profile manager.

Also prevent Tasks page lockups when switching to Active Operations and trigger failover refresh asynchronously to avoid QueueUpdateDraw re-entrancy.

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[devnullvoid]

Thank you for the contribution! I am reviewing

[devnullvoid]

Merged into develop — thank you again for the contribution and for opening the first substantial community PR.

We merged your feature and added a few follow-up hardening fixes on top before merge:

• fixed group/cluster mode lifecycle teardown to avoid stale background failover behavior during mode switches
• removed stale group_settings entries when deleting groups
• deduplicated aggregate-mode resources when multiple profiles point to the same cluster
• fixed placeholder behavior so connected deduped profiles do not create fake profile-named nodes (for example default)

This is now on the develop branch and will be included in the next release cycle.