feat(scheduler): Conntrack-Alert — silent-drop Warnung bevor Tabelle voll läuft — v1.1.108

- runConntrackCheck() liest /proc/sys/net/netfilter/nf_conntrack_count +
  nf_conntrack_max, feuert Warning bei ≥80% und Critical bei ≥90%
  (2-Min-Takt, 1h dedupe pro Severity-Key)
- Bei 100% Auslastung dropped nftables alle neuen Verbindungen lautlos;
  der Alert kommt damit rechtzeitig bevor das passiert
- conntrack.high-Trigger in beiden i18n-Dateien dokumentiert

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

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

@@ -1119,7 +1119,7 @@
     "title": "Health alerts",
     "intro": "Notification channels for critical events. Webhook (Slack/Discord/Teams/generic-HTTP) or email (SMTP). Triggers: cert.expiring (<14 d), cert.renew_failed, backup.failed, license.invalid.",
     "scopeTitle": "What triggers alerts?",
-    "scopeDesc": "cert.expiring — TLS cert <14 days remaining (12 h dedupe). cert.renew_failed — ACME renewer cycle had failures. backup.failed — scheduled backup couldn't run. license.invalid — License server returns valid=false. backend.down — all servers in a backend pool are DOWN (2 min check, 12 h dedupe). disk.full — root filesystem ≥80% warning, ≥90% critical (hourly check, 12 h dedupe). mem.high — RAM usage ≥85% warning, ≥95% critical (5 min check, 1 h dedupe).",
+    "scopeDesc": "cert.expiring — TLS cert <14 days remaining (12 h dedupe). cert.renew_failed — ACME renewer cycle had failures. backup.failed — scheduled backup couldn't run. license.invalid — License server returns valid=false. backend.down — all servers in a backend pool are DOWN (2 min check, 12 h dedupe). disk.full — root filesystem ≥80% warning, ≥90% critical (hourly check, 12 h dedupe). mem.high — RAM usage ≥85% warning, ≥95% critical (5 min check, 1 h dedupe). conntrack.high — conntrack table ≥80% warning, ≥90% critical; at 100% all new connections are silently dropped (2 min check, 1 h dedupe).",
     "tabs": { "channels": "Channels", "events": "History" },
     "add": "Add channel",
     "addTitle": "Add notification channel",