feat: umfangreiches UI+API-Polish (v1.1.36–1.1.42)

Backend:
- Audit-Log: Search-Endpoint mit ILIKE-Filter (actor/action/subject/date)
- NTP: /ntp/status via chronyc tracking (Stratum, Offset, Quelle)
- System: /service-restart mit Allowlist (haproxy/squid/unbound/chrony/scheduler)
- Domain-Response-Headers + Rate-Limit (Migration 0024)
- Join-Tokens (Migration 0025), Cluster-mTLS, Aggregator-Fan-Out
- apt-Service für Update-Banner (apt-get update + Versionsprüfung)
- Backup-Retry mit exponential backoff (retry_apt 3×)
- publish.sh fail-fast + cleanup-old.sh (max 10 Versionen)

Frontend:
- Audit-Log-Page (/audit) mit Filter + Pagination
- ErrorBoundary an React-Root + Vite build-target festgenagelt (iOS 15+)
- Storage-Schema-Stamp: auto-wipe bei Versions-Mismatch (blank-page-Fix)
- EmptyState-Komponente überall ausgerollt
- SSL: Aggregate-Karte (total/expiring/expired/errors)
- Backups: Aggregate-Karte (letzter Backup/Größe/Fehlschläge 24h) + Backup-Now
- NTP: Sync-Status-Karte (chronyc tracking live)
- Domains: Backend-UP/DOWN-Chip aus HAProxy-Stats
- Backends: HAProxy-Status-Spalte (UP/DEGRADED/DOWN)
- Settings: Service-Neustart-Karte (haproxy/squid/unbound/chrony/scheduler)
- Settings: Upgrade-Status-Card, Wartungsmodus, Auto-Update, Retention
- Dashboard: Recent-Alerts, Cluster-Health, License-Chip, Onboarding-Hint
- System-Regeln im Firewall als eigener Tab

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

internal/handlers/audit.go

@@ -22,9 +22,47 @@ func NewAuditHandler(repo *audit.Repo) *AuditHandler { return &AuditHandler{Repo
 func (h *AuditHandler) Register(rg *gin.RouterGroup) {
 	g := rg.Group("/audit")
 	g.GET("/recent", h.Recent)
+	g.GET("/search", h.Search)
 	g.GET("/live", h.Live)
 }
 
+// Search filtert audit_log nach Actor/Action/Subject/Date-Range.
+// Query-Params: actor, action, subject (alle ILIKE-Substring),
+// since/until (RFC3339), limit (max 500), offset.
+func (h *AuditHandler) Search(c *gin.Context) {
+	f := audit.SearchFilter{
+		Actor:   c.Query("actor"),
+		Action:  c.Query("action"),
+		Subject: c.Query("subject"),
+	}
+	if s := c.Query("since"); s != "" {
+		if t, err := time.Parse(time.RFC3339, s); err == nil {
+			f.Since = &t
+		}
+	}
+	if s := c.Query("until"); s != "" {
+		if t, err := time.Parse(time.RFC3339, s); err == nil {
+			f.Until = &t
+		}
+	}
+	if v := c.Query("limit"); v != "" {
+		if n, err := strconv.Atoi(v); err == nil {
+			f.Limit = n
+		}
+	}
+	if v := c.Query("offset"); v != "" {
+		if n, err := strconv.Atoi(v); err == nil {
+			f.Offset = n
+		}
+	}
+	rows, err := h.Repo.Search(c.Request.Context(), f)
+	if err != nil {
+		response.Internal(c, err)
+		return
+	}
+	response.OK(c, gin.H{"entries": rows, "limit": f.Limit, "offset": f.Offset})
+}
+
 // Recent returns the most recent audit_log entries — used by the
 // dashboard fallback path (z.B. wenn WebSocket nicht verbinden kann).
 // ?limit=N (1–100, default 10).