Make the app an installable PWA with phone layout and Web Push

Add a generated manifest, icon set, offline page and service worker that never caches authenticated HTML, plus install and update UI. Turn the rail into a drawer below md with container-query internals, dvh and safe-area handling, and reconnect the socket after visibility/network changes. Add Web Push subscriptions, presence-aware delivery, notification settings and tests.

src/dict/settings-pages-dict.ts

@@ -1,4 +1,5 @@
 import {
+    Bell,
     Bot,
     CpuAi,
     KeyRound,
@@ -43,6 +44,11 @@ export const SettingsPages: SettingsPage[] = [
         Icon: SlidersHorizontal,
     },
     { title: "Profile", url: "/admin/settings/profile", Icon: UserRound },
+    {
+        title: "Notifications",
+        url: "/admin/settings/notifications",
+        Icon: Bell,
+    },
     {
         title: "Change password",
         url: "/admin/settings/change-password",