v0.169.0: disk-health card + degradation notification (Lemezek állapota)

Consumes the agent v0.94.0 smart payload (MinAgent floor unchanged; feature-detect
by presence). One pure verdict fn agentapi.DiskVerdictFor shared by the dashboard
card and the 6h check. Card via a 60s /disks TTL cache (anti-smartctl-storm);
unreachable agent -> Nincs adat, page never blocks. disk-health-check (6h) emits
disk_health_degraded on a degradation only vs an in-memory baseline (first run
silent, recovery/UNKNOWN never notify, multi-attr -> one event). No global banner
(deliberate). Pairs with the hub allowlist bump.

Tests: verdict table (>=90 red-proof), notifier emit, check first-run-silent
(red-proof), degradation-once, recovery-silent, UNKNOWN-excluded, FAILING-critical,
nil-smart card, TTL cache.

controller/internal/web/templates/dashboard.html

@@ -110,6 +110,23 @@
 </div>
 {{end}}
 
+<div class="disk-health-card">
+    <h3>Lemezek állapota</h3>
+    {{if .DiskHealthRows}}
+    <ul class="disk-health-list">
+        {{range .DiskHealthRows}}
+        <li class="disk-health-row">
+            <span class="disk-health-label">{{.Label}}</span>
+            <span class="disk-health-status {{.ChipClass}}">{{.ChipLabel}}</span>
+            {{if .Temp}}<span class="disk-health-temp">{{.Temp}} °C</span>{{end}}
+        </li>
+        {{end}}
+    </ul>
+    {{else}}
+    <p class="form-hint state-text-neutral">Nincs adat</p>
+    {{end}}
+</div>
+
 {{if .BackupEnabled}}
 <div class="backup-status-card">
     <h3><a href="/backups" class="backup-card-link">Biztonsági mentés</a></h3>