Add comprehensive ZFS monitoring for FreeBSD servers

Implemented complete ZFS monitoring solution including ARC cache statistics,
pool health/capacity metrics, dataset usage, and I/O throughput monitoring.

Changes:
- Add ZFS recording rules (9 calculated metrics for ARC hit rates, memory usage, etc.)
- Add comprehensive Grafana dashboard with 19 panels across 5 rows:
  * Pool Overview: capacity, health, size, free space, usage trends
  * I/O Throughput: read/write operations and bytes per second
  * Dataset Statistics: table showing all datasets with usage details
  * ARC Cache Statistics: hit rates, size, memory usage
  * ARC Breakdown: data vs metadata, MRU vs MFU with pie charts
- Update Justfile to deploy ZFS recording rules
- Add textfile collector script on FreeBSD servers (f0, f1, f2) for pool/dataset metrics

Metrics collected:
- Pool: size, allocated, free, capacity %, health status
- I/O: read/write operations and throughput (via zpool iostat)
- Dataset: used, available, referenced space per filesystem
- ARC: hit rate, size, memory usage, data/metadata breakdown

Fixes:
- Pool health panel properly displays ONLINE/DEGRADED/FAULTED status
- All stat panels have correct options configuration

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

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