feat(dashboard): more System History metrics, persistence & localized labels

- Sample swap %, TCP/UDP connection counts and disk-usage % on the host ticker
- System History: Swap overlaid on the RAM tab, plus new Connections and Disk Usage tabs
- Persist the host time-series across restarts: gob snapshot beside the DB, written on a timer and at shutdown, restored on boot
- Live-refresh the open chart (2s for short ranges, 10s for longer)
- Localize CPU/RAM/Swap and the new tab/chart titles across all 13 languages and route legend series names through i18n

web/translation/ru-RU.json

@@ -128,12 +128,12 @@
     },
     "index": {
       "title": "Дашборд",
-      "cpu": "CPU",
+      "cpu": "ЦП",
       "logicalProcessors": "Логические процессоры",
       "frequency": "Частота",
-      "swap": "Swap",
+      "swap": "Подкачка",
       "storage": "Диск",
-      "memory": "RAM",
+      "memory": "Память",
       "threads": "Потоки",
       "xrayStatus": "Xray",
       "stopXray": "Стоп",
@@ -162,11 +162,15 @@
       "historyTitleDisk": "Дисковый ввод-вывод",
       "historyTitleOnline": "Клиенты онлайн",
       "historyTitleLoad": "Средняя нагрузка системы (1 / 5 / 15 мин)",
+      "historyTitleConnections": "Активные соединения (TCP / UDP)",
+      "historyTitleDiskUsage": "Использование дискового пространства",
       "historyTabBandwidth": "Пропускная способность",
       "historyTabPackets": "Пакеты",
       "historyTabDisk": "Диск I/O",
       "historyTabOnline": "Онлайн",
       "historyTabLoad": "Нагрузка",
+      "historyTabConnections": "Соединения",
+      "historyTabDiskUsage": "Использование диска",
       "charts": "Графики",
       "xrayMetricsTitle": "Метрики Xray",
       "xrayTitleHeap": "Выделенная память кучи",