feat(automations): implement model eligibility checks for automation creation

- Added model eligibility checks to ensure automations can only use billable models (premium or BYOK).
- Introduced new API endpoint to report model eligibility status for search spaces.
- Updated frontend components to display eligibility alerts and disable creation options when models are not billable.
- Enhanced automation creation forms to reflect model eligibility, preventing users from submitting invalid configurations.
- Implemented server-side logic to capture and preserve model preferences across automation edits, ensuring consistent behavior during execution.

surfsense_backend/app/automations/services/__init__.py

@@ -3,14 +3,26 @@
 from __future__ import annotations
 
 from .automation import AutomationService, get_automation_service
+from .model_policy import (
+    AutomationModelPolicyError,
+    assert_automation_models_billable,
+    assert_models_billable,
+    get_automation_model_eligibility,
+    get_model_eligibility,
+)
 from .run import RunService, get_run_service
 from .trigger import TriggerService, get_trigger_service
 
 __all__ = [
+    "AutomationModelPolicyError",
     "AutomationService",
     "RunService",
     "TriggerService",
+    "assert_automation_models_billable",
+    "assert_models_billable",
+    "get_automation_model_eligibility",
     "get_automation_service",
+    "get_model_eligibility",
     "get_run_service",
     "get_trigger_service",
 ]