feat(automation): register agent_task action and schedule/manual triggers

surfsense_backend/app/automations/registries/triggers/schedule.py

@@ -0,0 +1,21 @@
+"""Built-in ``schedule`` trigger. Self-registers at import time."""
+
+from __future__ import annotations
+
+from app.automations.schemas.triggers import ScheduleTriggerParams
+
+from .store import register_trigger
+from .types import TriggerDefinition
+
+SCHEDULE_TRIGGER = TriggerDefinition(
+    type="schedule",
+    description="Fire on a cron schedule in a given timezone.",
+    params_schema=ScheduleTriggerParams.model_json_schema(),
+    payload_schema={
+        "type": "object",
+        "additionalProperties": False,
+        "properties": {},
+    },
+)
+
+register_trigger(SCHEDULE_TRIGGER)