Improve user editing, allowing admins access to all stores without assignment

Updates user editing logic to handle admin roles and store access, with schema changes.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 91318273-c764-4fd4-be04-bdc12c38af32
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/0715008c-7244-40f4-befc-26c014852236/9d9e1107-c416-4124-a939-a91c612c56a1.jpg

server/routes.ts

@@ -295,7 +295,7 @@ export async function registerRoutes(app: Express): Promise<Server> {
       const userData = insertUserSchema.partial().parse(req.body);
       
       // Protection spécifique pour le rôle seulement
-      if (userData.role) {
+      if (userData.role !== undefined) {
         // Protection : empêcher un admin de changer son propre rôle par accident
         if (userId === currentUser?.id && userData.role !== 'administrator') {
           return res.status(400).json({