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/css/style.css

@@ -633,6 +633,75 @@ main {
     color: white;
 }
 
+/* HA Summary */
+.ha-summary {
+    font-size: 12px;
+    line-height: 1.6;
+    margin-bottom: 8px;
+}
+
+.ha-stat {
+    padding: 2px 0;
+    color: var(--text-secondary);
+}
+
+/* Notification Matrix */
+.notify-channels {
+    display: grid;
+    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
+    gap: 12px;
+    margin-bottom: 20px;
+}
+
+.notify-table {
+    width: 100%;
+    border-collapse: collapse;
+    font-size: 14px;
+}
+
+.notify-table th,
+.notify-table td {
+    padding: 10px 12px;
+    text-align: center;
+    border-bottom: 1px solid var(--border);
+}
+
+.notify-table th {
+    font-size: 12px;
+    color: var(--text-secondary);
+    text-transform: uppercase;
+    letter-spacing: 0.5px;
+}
+
+.notify-table td:first-child,
+.notify-table th:first-child {
+    text-align: left;
+}
+
+.notify-table input[type="checkbox"] {
+    width: 18px;
+    height: 18px;
+    cursor: pointer;
+    accent-color: var(--accent);
+}
+
+/* Small button */
+.btn-sm {
+    padding: 6px 14px;
+    font-size: 12px;
+    border: 1px solid var(--border);
+    border-radius: 6px;
+    background: var(--bg-primary);
+    color: var(--text-primary);
+    cursor: pointer;
+    transition: background 0.2s;
+}
+
+.btn-sm:hover {
+    background: var(--accent);
+    color: white;
+}
+
 /* Footer */
 .app-footer {
     text-align: center;
@@ -660,4 +729,7 @@ main {
     .stats-bar { flex-direction: column; gap: 8px; }
     header { padding: 12px 16px; }
     .header-right { gap: 4px; }
+    .tabs { flex-wrap: wrap; }
+    .tab { flex: 0 1 auto; padding: 8px 12px; font-size: 12px; }
+    .notify-channels { grid-template-columns: 1fr; }
 }