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/readable-stream/readable.js

@@ -0,0 +1,19 @@
+var Stream = require('stream');
+if (process.env.READABLE_STREAM === 'disable' && Stream) {
+  module.exports = Stream;
+  exports = module.exports = Stream.Readable;
+  exports.Readable = Stream.Readable;
+  exports.Writable = Stream.Writable;
+  exports.Duplex = Stream.Duplex;
+  exports.Transform = Stream.Transform;
+  exports.PassThrough = Stream.PassThrough;
+  exports.Stream = Stream;
+} else {
+  exports = module.exports = require('./lib/_stream_readable.js');
+  exports.Stream = Stream || exports;
+  exports.Readable = exports;
+  exports.Writable = require('./lib/_stream_writable.js');
+  exports.Duplex = require('./lib/_stream_duplex.js');
+  exports.Transform = require('./lib/_stream_transform.js');
+  exports.PassThrough = require('./lib/_stream_passthrough.js');
+}