feat: add Synology NAS, Home Assistant monitoring, multi-channel notifications

New tabs:
- Synology NAS: CPU, RAM, temp, volumes, VMs, Docker containers
- Home Assistant: sensors, automations, persons, climate, battery, doors

New features:
- Personalized PC agent download with custom name
- Notification settings: per-category Telegram/Email/WhatsApp toggles
- Email via SMTP, WhatsApp via CallMeBot API
- Test notification buttons for each channel
- Unified notifier replaces direct Telegram calls in alerter

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

server/static/js/i18n.js

@@ -73,6 +73,8 @@ const translations = {
         instr_api: "API endpoints",
         instr_thresholds: "Пороги алертов",
         instr_thresholds_text: "Настройки → Мониторинг. По умолчанию: CPU 90%, RAM 90%, Disk 90%",
+        tabServers: "Серверы",
+        tabPC: "ПК",
     },
     en: {
         title: "VPS Monitoring",
@@ -148,6 +150,8 @@ const translations = {
         instr_api: "API endpoints",
         instr_thresholds: "Alert thresholds",
         instr_thresholds_text: "Settings → Monitoring. Default: CPU 90%, RAM 90%, Disk 90%",
+        tabServers: "Servers",
+        tabPC: "PC",
     }
 };