fix(excel): move datasheet generation to post-deploy and add persistent volume

docker-compose.yml

@@ -14,6 +14,7 @@ services:
       PAYLOAD_SECRET: ${PAYLOAD_SECRET:-fallback-secret-for-production-needs-change}
     volumes:
       - klz_media_data:/app/public/media
+      - klz_datasheets:/app/public/datasheets
     labels:
       - "traefik.enable=true"
       # HTTP ⇒ HTTPS redirect
@@ -111,3 +112,5 @@ volumes:
     external: false
   klz_media_data:
     external: false
+  klz_datasheets:
+    external: false