Add continuous hardware health monitoring and component detail view

- kmsg watcher now records kernel errors (GPU Xid, MCE, EDAC, storage I/O) at all times,
  not only during SAT tasks; flushImmediate writes directly to ComponentStatusDB
- New health_poller: polls ipmitool sdr every 60s for PSU health (watchdog:psu source)
- Hardware Summary card auto-refreshes every 30s via htmx without page reload
- Component rows (CPU/Memory/Storage/GPU/PSU) are now clickable -- opens a modal
  with per-component status, source, timestamp and last 20 history entries

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

audit/internal/webui/health_poller.go

@@ -0,0 +1,76 @@
+package webui
+
+import (
+	"bytes"
+	"context"
+	"log/slog"
+	"os/exec"
+	"time"
+
+	"bee/audit/internal/app"
+	"bee/audit/internal/collector"
+)
+
+const healthPollInterval = 60 * time.Second
+const psuIPMITimeout = 15 * time.Second
+
+// healthPoller runs periodic health checks for hardware components that do not
+// emit kernel log events (e.g. PSU). Results are written to ComponentStatusDB.
+type healthPoller struct {
+	statusDB *app.ComponentStatusDB
+}
+
+func newHealthPoller(statusDB *app.ComponentStatusDB) *healthPoller {
+	return &healthPoller{statusDB: statusDB}
+}
+
+func (p *healthPoller) start() {
+	goRecoverLoop("health poller", 5*time.Second, p.run)
+}
+
+func (p *healthPoller) run() {
+	ticker := time.NewTicker(healthPollInterval)
+	defer ticker.Stop()
+	for range ticker.C {
+		p.pollPSU()
+	}
+}
+
+func (p *healthPoller) pollPSU() {
+	if p.statusDB == nil {
+		return
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), psuIPMITimeout)
+	defer cancel()
+
+	cmd := exec.CommandContext(ctx, "ipmitool", "sdr")
+	var out bytes.Buffer
+	cmd.Stdout = &out
+	if err := cmd.Run(); err != nil {
+		// IPMI not available or not a server — skip silently.
+		slog.Debug("health poller: ipmitool sdr unavailable", "err", err)
+		return
+	}
+
+	slots := collector.PSUSlotsFromSDR(out.String())
+	if len(slots) == 0 {
+		return
+	}
+
+	const source = "watchdog:psu"
+	for slot, psu := range slots {
+		key := "psu:" + slot
+		status := psu.Status
+		if status == "" {
+			status = "Unknown"
+		}
+		detail := ""
+		switch status {
+		case "Critical":
+			detail = "PSU sensor reported non-OK state"
+		case "Warning":
+			detail = "PSU sensor in warning state"
+		}
+		p.statusDB.Record(key, source, status, detail)
+	}
+}