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/ieee754/index.d.ts

@@ -0,0 +1,10 @@
+declare namespace ieee754 {
+    export function read(
+        buffer: Uint8Array, offset: number, isLE: boolean, mLen: number,
+        nBytes: number): number;
+    export function write(
+        buffer: Uint8Array, value: number, offset: number, isLE: boolean,
+        mLen: number, nBytes: number): void;
+  }
+  
+  export = ieee754;