When Pulse runs in a container (LXC/Docker), the setup script would claim
temperature monitoring was enabled on cluster nodes, but Pulse couldn't
actually SSH to them. The script ran on the Proxmox host which could SSH
fine, but didn't verify connectivity from Pulse itself.
Changes:
- Added /api/system/verify-temperature-ssh endpoint that tests SSH from Pulse
- Setup script now calls this endpoint after configuring cluster nodes
- Detects when Pulse is containerized and provides ProxyJump config instructions
- Shows clear success/failure status for each node
Addresses #528