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

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

@@ -0,0 +1,17 @@
+"""Built-in ``manual`` trigger. Self-registers at import time."""
+
+from __future__ import annotations
+
+from app.automations.schemas.triggers import ManualTriggerParams
+
+from .store import register_trigger
+from .types import TriggerDefinition
+
+MANUAL_TRIGGER = TriggerDefinition(
+    type="manual",
+    description="Fire on a user-initiated 'Run now' invocation.",
+    params_schema=ManualTriggerParams.model_json_schema(),
+    payload_schema={"type": "object"},
+)
+
+register_trigger(MANUAL_TRIGGER)