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>

management-ui/src/i18n/locales/de/common.json

@@ -399,6 +399,25 @@
       "api": "API",
       "ifaces": "Interfaces",
       "wg": "WireGuard"
+    },
+    "servicesCard": {
+      "title": "Service-Status (live, 10s)"
+    },
+    "activityCard": {
+      "title": "Letzte Aktivität (Audit-Log)",
+      "empty": "Noch keine Aktivität — Mutationen werden hier protokolliert."
+    },
+    "haproxyCard": {
+      "title": "HAProxy-Backends (live)",
+      "empty": "Keine Backend-Stats erreichbar (HAProxy down oder admin.sock-permission)."
+    },
+    "resCard": {
+      "load": "Load",
+      "memory": "Memory",
+      "disk": "Disk /",
+      "free": "frei",
+      "conntrack": "Conntrack",
+      "uptime": "Uptime"
     }
   },
   "ntp": {