Use celery tasks instead of systemd timers for periodic work; and add more tests

kick/tasks.py

@@ -0,0 +1,17 @@
+from __future__ import annotations
+
+import logging
+
+from celery import shared_task
+from django.core.management import call_command
+
+logger = logging.getLogger("ttvdrops.tasks")
+
+
+@shared_task(bind=True, queue="api-fetches", max_retries=3, default_retry_delay=120)
+def import_kick_drops(self) -> None:  # noqa: ANN001
+    """Fetch and upsert Kick drop campaigns from the public API."""
+    try:
+        call_command("import_kick_drops")
+    except Exception as exc:
+        raise self.retry(exc=exc) from exc