Add Redis scan_keys iterator API.

Provide a SCAN-based key iterator for Redis adapters so callers can enumerate large keyspaces without relying on blocking KEYS lookups.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/unit/json_repository_interface_test.py

@@ -80,3 +80,24 @@ def test_instantiation_fails_when_list_keys_not_implemented() -> None:
 
     with pytest.raises(TypeError):
         _ = Incomplete()  # type: ignore
+
+
+def test_scan_keys_defaults_to_list_keys() -> None:
+    """Test that the default scan_keys implementation delegates to list_keys."""
+
+    class Complete(JsonRepositoryInterface):
+        def get(self, key: str) -> dict | None:
+            return None
+
+        def set(self, key: str, data: dict) -> None:
+            pass
+
+        def delete(self, key: str) -> None:
+            pass
+
+        def list_keys(self, pattern: str) -> list[str]:
+            return [f"{pattern}-1", f"{pattern}-2"]
+
+    repository = Complete()
+
+    assert list(repository.scan_keys("user")) == ["user-1", "user-2"]