deploy: purge .next before build; CI also restarts Convex service to ensure fresh state

.github/workflows/ci-cd-web-desktop.yml

@@ -80,6 +80,11 @@ jobs:
         run: |
           docker service update --force sistema_web || true
 
+      - name: (Optional) Restart Convex backend service
+        if: ${{ hashFiles(format('{0}/stack.yml', env.APP_DIR)) != '' }}
+        run: |
+          docker service update --force sistema_convex_backend || true
+
   convex_deploy:
     name: Deploy Convex functions
     needs: [deploy, changes]