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/tar/lib/strip-trailing-slashes.js

@@ -0,0 +1,13 @@
+// warning: extremely hot code path.
+// This has been meticulously optimized for use
+// within npm install on large package trees.
+// Do not edit without careful benchmarking.
+module.exports = str => {
+  let i = str.length - 1
+  let slashesStart = -1
+  while (i > -1 && str.charAt(i) === '/') {
+    slashesStart = i
+    i--
+  }
+  return slashesStart === -1 ? str : str.slice(0, slashesStart)
+}