Add system for managing and scheduling data backups

Introduce a new backup management feature with automated scheduling, manual backups, and a dedicated interface for viewing backup status and details. This includes integrating `node-cron` for scheduling, updating the database schema to store backup information, and creating new routes and components for the backup manager.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 7c468936-2a88-4686-ac0a-84921a45222d
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/1957c339-2757-4d1f-8e92-e9f71a1ce58e/7c468936-2a88-4686-ac0a-84921a45222d/9xfbVBU

client/src/components/Sidebar.tsx

@@ -146,6 +146,12 @@ export default function Sidebar() {
       icon: UserCog, 
       roles: ["admin"] 
     },
+    { 
+      path: "/backup", 
+      label: "Sauvegardes", 
+      icon: Database, 
+      roles: ["admin"] 
+    },
     { 
       path: "/nocodb-config", 
       label: "Configuration NocoDB",