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/math-intrinsics/sign.js

@@ -0,0 +1,11 @@
+'use strict';
+
+var $isNaN = require('./isNaN');
+
+/** @type {import('./sign')} */
+module.exports = function sign(number) {
+	if ($isNaN(number) || number === 0) {
+		return number;
+	}
+	return number < 0 ? -1 : +1;
+};