Improves user experience when physical disks don't appear by providing
clear, context-aware instructions. The empty state now shows:
- When no PVE nodes are configured: prompt to add nodes
- When nodes exist but no disks appear: step-by-step requirements
including enabling SMART monitoring in both Pulse and Proxmox
This addresses confusion from issue #594 where users didn't realize
they needed to enable SMART monitoring in Proxmox itself (not just
in Pulse settings) and wait 5 minutes for data collection.
Related to #594
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