seed: planned Scaleway backup store for WP-0002

Identity, topology, consumer bindings, and the planned attribute file
(region nl-ams, endpoint/bucket still null). Post-purchase fill is
REEF-STORAGE-WP-0002.

substrate/identity.yaml

@@ -0,0 +1,14 @@
+reef_id: reef-storage
+display_name: Railiance delegated object storage
+substrate_kind: object-storage
+ownership_repo: railiance-platform
+lifecycle_state: planned
+criticality: high
+primary_rail: null
+current_members: []
+current_role: Provider-delegated S3-compatible store. Scaleway operates the capability; this reef names the boundary and non-secret attributes.
+source_of_truth:
+  repo: reef-storage
+  paths:
+    - declarations/reef.yaml
+    - substrate/object-stores/platform-audit-storage.yaml