fix(flowiseai): update_script: switch npm to pnpm, fix service ExecStart

- Use pnpm add -g instead of npm install -g (apify-client enforces pnpm)
- Call setup_nodejs to ensure pnpm is available in existing containers
- Migrate ExecStart from 'npx flowise start' to 'flowise start' in
  existing installations on update

ct/flowiseai.sh

@@ -29,7 +29,12 @@ function update_script() {
   fi
   msg_info "Updating FlowiseAI (this may take some time)"
   systemctl stop flowise
-  $STD npm install -g flowise --upgrade
+  NODE_VERSION="20" NODE_MODULE="pnpm" setup_nodejs
+  $STD pnpm add -g flowise
+  if grep -q 'ExecStart=npx flowise start' /etc/systemd/system/flowise.service; then
+    sed -i 's|ExecStart=npx flowise start|ExecStart=flowise start|' /etc/systemd/system/flowise.service
+    systemctl daemon-reload
+  fi
   systemctl start flowise
   msg_ok "Updated FlowiseAI"
   msg_ok "Updated successfully!"