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/server.go

@@ -149,6 +149,13 @@ type Server struct {
 	// manual trigger goes through the loop (stop stacks → backup → resume), never a bare agent call.
 	backupTrigger BackupTrigger
 
+	// Disk-health card + 6h degradation check (v0.169.0). diskHealth holds the 60s /disks TTL cache +
+	// the in-memory verdict baseline. disksFn / diskNotifyFn are test seams (nil → the real agent
+	// client Disks() / the real notifier).
+	diskHealth   diskHealthState
+	disksFn      func(context.Context) (agentapi.DisksResponse, error)
+	diskNotifyFn func(label string, attrs []string, critical bool)
+
 	// App-email SMTP shim lifecycle (optional — nil when no hub is configured or the kill-switch is
 	// off). The global app-email settings toggle calls Apply() so the shim starts/stops at runtime.
 	mailShim MailShimController