feat(scheduler+ntp): Memory-Alerts + NTP-Status freq/rms — v1.1.107

- Scheduler: runMemoryCheck() liest /proc/meminfo, feuert Warning bei ≥85% und Critical bei ≥95% RAM-Auslastung (5-Min-Intervall, 1h dedupe pro Severity-Key)
- NTP-Status-Karte: freq_ppm (±ppm mit Warnung bei >100) und rms_offset_ms werden jetzt angezeigt — Felder waren im Backend schon vorhanden, aber nie gerendert
- Alerts scopeDesc: mem.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

@@ -837,6 +837,9 @@
       "stratum": "Stratum",
       "offset": "Offset",
       "offsetHint": "Time difference to reference source. Values > 100 ms are unusual — check network or misconfigured source.",
+      "freqPpm": "Freq. error",
+      "freqPpmHint": "Frequency error of the local clock vs. reference. Values > ±100 ppm indicate a drifting clock or hardware issue.",
+      "rmsOffset": "RMS offset",
       "loading": "Loading…"
     },
     "pool": {
@@ -1116,7 +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).",
+    "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).",
     "tabs": { "channels": "Channels", "events": "History" },
     "add": "Add channel",
     "addTitle": "Add notification channel",