feat: backend service

backend/docs/README.md

@@ -0,0 +1,22 @@
+# Backend Service Docs
+
+This directory keeps service-local documentation that is too detailed for
+the workspace-level architecture document and too diagram-heavy for the
+module README.
+
+Sections:
+
+- [Runtime and components](runtime.md)
+- [Domain and protocol flows](flows.md)
+- [Operator runbook](runbook.md)
+- [Configuration and contract examples](examples.md)
+
+Primary references:
+
+- [`../README.md`](../README.md) — service scope, contracts,
+  configuration, operational behaviour.
+- [`../openapi.yaml`](../openapi.yaml) — REST contract.
+- [`../PLAN.md`](../PLAN.md) — historical staged build-up; kept for
+  archaeology, not as a source of truth.
+- [`../../ARCHITECTURE.md`](../../ARCHITECTURE.md) — workspace-level
+  architecture.