check_disk_space periodic task should db.close_old_connections() after running

[medihack]

The pattern is already established elsewhere in adit.core.tasks and adit.mass_transfer.tasks (linked to procrastinate-org/procrastinate#1106). check_disk_space queries DicomFolder.objects.all() and currently doesn't close the connection at the end, leaking a Django per-thread connection into the asgiref sync_to_async worker thread.

In production it accumulates over time; in tests it contributes to the test-DB-teardown warning addressed by openradx/adit-radis-shared#197.

Proposed fix

from django import db

@app.periodic(cron="0 7 * * *")
@app.task
def check_disk_space(*args, **kwargs):
    try:
        # ... existing body ...
    finally:
        db.close_old_connections()

Same try/finally pattern as the other ADIT tasks that link to procrastinate#1106.

Audit

A grep across adit/*/tasks.py to catch any other periodic or task functions using ORM without db.close_old_connections() would be worthwhile while addressing this one.