Add publish preview retention policy, normalize refresh/cached contract, and add storage audit and cleanup admin endpoints

backend/app/repositories/scheme_artifacts.py

@@ -59,6 +59,28 @@ async def list_scheme_artifacts(
         return list(result.scalars().all())
 
 
+async def list_artifacts_by_type(
+    *,
+    artifact_type: str,
+    artifact_variant: str | None = None,
+) -> list[SchemeArtifactRecord]:
+    async with AsyncSessionLocal() as session:
+        stmt = select(SchemeArtifactRecord).where(
+            SchemeArtifactRecord.artifact_type == artifact_type
+        )
+
+        if artifact_variant is not None:
+            stmt = stmt.where(SchemeArtifactRecord.artifact_variant == artifact_variant)
+
+        stmt = stmt.order_by(
+            asc(SchemeArtifactRecord.created_at),
+            asc(SchemeArtifactRecord.id),
+        )
+
+        result = await session.execute(stmt)
+        return list(result.scalars().all())
+
+
 async def artifact_exists(
     *,
     scheme_version_id: str,