Server stats - idle SQL queries

I've had some users (who had admin) report that there are queries running.

These are idle queries presumably due to connection pooling

Have idle eg:

```
pid Duration Query State
57395 10m SELECT "django_migrations"."id", "django_migrations"."app", "django_migrations"."name", "django_migrations"."applied" FROM "django_migrations" idle
58601 9m 36s UPDATE "upload_uploadstep" SET "celery_task" = '95e08b35-7d21-447d-a48a-659c1c4fbf06' WHERE "upload_uploadstep"."id" = 2992 idle
```

**FIXES**

* Dumbest way would be just filter for "idle"
* Perhaps if we use new [Django 5.1 has connection pooling, mentioned in recommended Django fixes](https://github.com/SACGF/variantgrid_private/issues/3756) it could fix it