feat: make output types workflow-first contracts

backend/app/models/output_type.py

@@ -1,3 +1,13 @@
 # Compat shim — use app.domains.rendering.models instead
-from app.domains.rendering.models import OutputType, VALID_RENDER_BACKENDS
-__all__ = ["OutputType", "VALID_RENDER_BACKENDS"]
+from app.domains.rendering.models import (
+    OUTPUT_TYPE_ARTIFACT_KINDS,
+    OUTPUT_TYPE_WORKFLOW_FAMILIES,
+    OutputType,
+    VALID_RENDER_BACKENDS,
+)
+__all__ = [
+    "OutputType",
+    "VALID_RENDER_BACKENDS",
+    "OUTPUT_TYPE_WORKFLOW_FAMILIES",
+    "OUTPUT_TYPE_ARTIFACT_KINDS",
+]