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/mkdirp/bin/usage.txt

@@ -0,0 +1,12 @@
+usage: mkdirp [DIR1,DIR2..] {OPTIONS}
+
+  Create each supplied directory including any necessary parent directories that
+  don't yet exist.
+  
+  If the directory already exists, do nothing.
+
+OPTIONS are:
+
+  -m, --mode   If a directory needs to be created, set the mode as an octal
+               permission string.
+