Adds a real-time I/O utilization column to the Main page array and pool device tables. Each disk row shows a live activity bar (0-100%) updated every 2 seconds. Supports Array Devices, Pool Devices (including ZFS pools), and Boot Device. Summary rows display the average activity across all pool members. Three display modes: progress bar, colored percentage, or plain text. Configurable averaging window: Instant (2s), 10 seconds, 1 minute, or 5 minutes.