feat(dashboard): Operations-Dashboard mit Live-Health/Resources/Audit/HAProxy

Vorher: Dashboard war Counts + statische Cards. Jetzt operativer
Überblick — was läuft, was klemmt, was wurde gerade geändert.

Backend (4 neue Endpoints):
* GET /api/v1/system/services — systemctl is-active für 8 services
  (edgeguard-api, scheduler, haproxy, nftables, unbound, chrony,
  squid, postgresql). Inklusive ActiveEnterTimestamp.
* GET /api/v1/system/resources — /proc/loadavg, meminfo, statfs(/),
  nf_conntrack count+max, uptime.
* GET /api/v1/audit/recent?limit=N — letzte audit_log entries.
  audit-Repo bekommt ListRecent + Entry struct.
* GET /api/v1/haproxy/stats — parsed haproxy 'show stat' CSV vom
  /run/haproxy/admin.sock (postinst addet edgeguard zu haproxy-
  group für socket-read; haproxy-group exists nach apt install).

Frontend Dashboard rewrite:
* PageHeader + KPI-Strip (6 tiles, wie zuvor) — bleibt.
* Resources-Strip: Load (1/5/15) + Mem-Progress + Disk-Progress +
  Conntrack-Progress + Uptime.
* Service-Health-Grid: 8 Karten mit StatusDot + state.
* Recent-Activity-Card (audit-log): action-Tag + actor + subject +
  relative time.
* HAProxy-Backends-Card: backend/server + UP/DOWN-Tag + sessions +
  bytes_in/out + last_change_age.
* WireGuard live (handshake-age, traffic) — bleibt aus früherem
  Stand.
* Cluster + Firewall + SSL + Routing Cards — bleiben.
* Polling 10s für services/resources/haproxy, 15s für audit.

Plus: postinst usermod -a -G haproxy edgeguard für admin.sock
read-permission.

Version 1.0.43.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/handlers/audit.go

@@ -0,0 +1,38 @@
+package handlers
+
+import (
+	"strconv"
+
+	"github.com/gin-gonic/gin"
+
+	"git.netcell-it.de/projekte/edgeguard-native/internal/handlers/response"
+	"git.netcell-it.de/projekte/edgeguard-native/internal/services/audit"
+)
+
+type AuditHandler struct {
+	Repo *audit.Repo
+}
+
+func NewAuditHandler(repo *audit.Repo) *AuditHandler { return &AuditHandler{Repo: repo} }
+
+func (h *AuditHandler) Register(rg *gin.RouterGroup) {
+	g := rg.Group("/audit")
+	g.GET("/recent", h.Recent)
+}
+
+// Recent returns the most recent audit_log entries — used by the
+// dashboard's recent-activity card. ?limit=N (1–100, default 10).
+func (h *AuditHandler) Recent(c *gin.Context) {
+	limit := 10
+	if v := c.Query("limit"); v != "" {
+		if n, err := strconv.Atoi(v); err == nil {
+			limit = n
+		}
+	}
+	rows, err := h.Repo.ListRecent(c.Request.Context(), limit)
+	if err != nil {
+		response.Internal(c, err)
+		return
+	}
+	response.OK(c, gin.H{"entries": rows})
+}