feat: complete ZFS pool monitoring implementation (addresses #423)

- Implement proper API integration with list and detail endpoints
- Add ZFS pool and device status conversion
- Enable by default with PULSE_DISABLE_ZFS_MONITORING opt-out
- Test with real Proxmox nodes and verify functionality
- Add comprehensive error handling and logging
- Document feature configuration and requirements

The feature now properly:
- Fetches ZFS pool status from Proxmox API
- Detects degraded/faulted pools and devices
- Tracks read/write/checksum errors
- Generates appropriate alerts
- Displays issues in the Storage tab UI

Tested and verified working with real Proxmox clusters.

docs/zfs-monitoring.md

@@ -0,0 +1,98 @@
+# ZFS Pool Monitoring
+
+Pulse v4.15.0+ includes automatic ZFS pool health monitoring for Proxmox VE nodes.
+
+## Features
+
+- **Automatic Detection**: Detects ZFS storage and monitors associated pools
+- **Health Status**: Monitors pool state (ONLINE, DEGRADED, FAULTED)
+- **Error Tracking**: Tracks read, write, and checksum errors
+- **Device Monitoring**: Monitors individual devices within pools
+- **Alert Generation**: Creates alerts for degraded pools and device errors
+- **Frontend Display**: Shows ZFS issues inline with storage information
+
+## Requirements
+
+### Proxmox Permissions
+The Pulse user needs `Sys.Audit` permission on `/nodes/{node}/disks` to access ZFS information:
+
+```bash
+# Grant permission for ZFS monitoring (already included in standard Pulse role)
+pveum acl modify /nodes -user pulse-monitor@pam -role PVEAuditor
+```
+
+### API Endpoints Used
+- `/nodes/{node}/disks/zfs` - Lists ZFS pools
+- `/nodes/{node}/disks/zfs/{pool}` - Gets detailed pool status
+
+## Configuration
+
+ZFS monitoring is **enabled by default** in Pulse v4.15.0+.
+
+### Disabling ZFS Monitoring
+If you want to disable ZFS monitoring (e.g., for performance reasons):
+
+```bash
+# Add to /opt/pulse/.env or environment
+PULSE_DISABLE_ZFS_MONITORING=true
+```
+
+## Alert Types
+
+### Pool State Alerts
+- **Warning**: Pool is DEGRADED
+- **Critical**: Pool is FAULTED or UNAVAIL
+
+### Error Alerts
+- **Warning**: Any read/write/checksum errors detected
+- Alerts include error counts and affected devices
+
+### Device Alerts
+- **Warning**: Device has errors but is ONLINE
+- **Critical**: Device is FAULTED or UNAVAIL
+
+## Frontend Display
+
+ZFS issues appear in the Storage tab:
+- Yellow warning bar for degraded pools
+- Red error counts for devices with issues
+- Detailed device status for troubleshooting
+
+## Performance Impact
+
+- Adds 2 API calls per node with ZFS storage
+- Typically adds <1 second to polling cycle
+- Only queries nodes that have ZFS storage
+
+## Troubleshooting
+
+### No ZFS Data Appearing
+1. Check permissions: `pveum user permissions pulse-monitor@pam`
+2. Verify ZFS pools exist: `zpool list`
+3. Check logs: `grep ZFS /opt/pulse/pulse.log`
+
+### Permission Denied Errors
+Grant the required permission:
+```bash
+pveum acl modify /nodes -user pulse-monitor@pam -role PVEAuditor
+```
+
+### High API Load
+Disable ZFS monitoring if not needed:
+```bash
+echo "PULSE_DISABLE_ZFS_MONITORING=true" >> /opt/pulse/.env
+systemctl restart pulse-backend
+```
+
+## Example Alert
+
+```
+Alert: ZFS pool 'rpool' is DEGRADED
+Node: pve1
+Pool: rpool
+State: DEGRADED
+Errors: 12 read, 0 write, 3 checksum
+Device sdb2: DEGRADED with 12 read errors
+```
+
+This helps administrators identify failing drives before complete failure occurs.