Marketing Hub: RBAC, i18n (AR/EN), tasks overhaul, team/user merge, tutorial

Features:
- Full RBAC with 3 roles (superadmin/manager/contributor)
- Ownership tracking on posts, tasks, campaigns, projects
- Task system: assign to anyone, filter combobox, visibility scoping
- Team members merged into users table (single source of truth)
- Post thumbnails on kanban cards from attachments
- Publication link validation before publishing
- Interactive onboarding tutorial with Settings restart
- Full Arabic/English i18n with RTL layout support
- Language toggle in sidebar, IBM Plex Sans Arabic font
- Brand-based visibility filtering for non-superadmins
- Manager can only create contributors
- Profile completion flow for new users
- Cookie-based sessions (express-session + SQLite)

server/node_modules/side-channel/index.d.ts

@@ -0,0 +1,14 @@
+import getSideChannelList from 'side-channel-list';
+import getSideChannelMap from 'side-channel-map';
+import getSideChannelWeakMap from 'side-channel-weakmap';
+
+declare namespace getSideChannel {
+	type Channel<K, V> =
+		| getSideChannelList.Channel<K, V>
+		| ReturnType<Exclude<typeof getSideChannelMap<K, V>, false>>
+		| ReturnType<Exclude<typeof getSideChannelWeakMap<K, V>, false>>;
+}
+
+declare function getSideChannel<K, V>(): getSideChannel.Channel<K, V>;
+
+export = getSideChannel;