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/mimic-response/index.d.ts

@@ -0,0 +1,17 @@
+import {IncomingMessage} from 'http';
+
+/**
+Mimic a [Node.js HTTP response stream](https://nodejs.org/api/http.html#http_class_http_incomingmessage)
+
+Makes `toStream` include the properties from `fromStream`.
+
+@param fromStream - The stream to copy the properties from.
+@param toStream - The stream to copy the properties to.
+@return The same object as `toStream`.
+*/
+declare function mimicResponse<T extends NodeJS.ReadableStream>(
+	fromStream: IncomingMessage, // eslint-disable-line @typescript-eslint/prefer-readonly-parameter-types
+	toStream: T,
+): T & IncomingMessage;
+
+export = mimicResponse;