feat(09-10): add typed relation manager

.planning/milestone.lock

@@ -0,0 +1,6 @@
+{
+  "phase": "09",
+  "session": "codex-thread-id-01a0d740-5347-7f00-9bb6-24c3bbe01139",
+  "pid": 30,
+  "updated_at": 1790317872927
+}

.planning/state.json

@@ -0,0 +1,88 @@
+{
+  "contract": "1.0.0",
+  "flavor": "core",
+  "milestone": "v1.0",
+  "phases": [
+    {
+      "number": "1",
+      "name": "Framework kernel foundation",
+      "status": "complete"
+    },
+    {
+      "number": "2",
+      "name": "API parity harness bootstrap",
+      "status": "complete"
+    },
+    {
+      "number": "3",
+      "name": "First vertical slice — genres end to end",
+      "status": "complete"
+    },
+    {
+      "number": "4",
+      "name": "CLI scaffolding, i18n and mail",
+      "status": "complete"
+    },
+    {
+      "number": "5",
+      "name": "Data layer full fidelity",
+      "status": "complete"
+    },
+    {
+      "number": "6",
+      "name": "HTTP routing, auth groups and rate limiting",
+      "status": "complete"
+    },
+    {
+      "number": "7",
+      "name": "User plugin and authentication",
+      "status": "complete"
+    },
+    {
+      "number": "8",
+      "name": "OAuth2.1 authorization server",
+      "status": "complete"
+    },
+    {
+      "number": "9",
+      "name": "Backend admin authentication and schema pipeline",
+      "status": "in_progress"
+    },
+    {
+      "number": "10",
+      "name": "Admin Vue SPA",
+      "status": "pending"
+    },
+    {
+      "number": "11",
+      "name": "Jobs, realtime and search infrastructure",
+      "status": "pending"
+    },
+    {
+      "number": "12",
+      "name": "Płytarium API — Collections and Albums",
+      "status": "pending"
+    },
+    {
+      "number": "13",
+      "name": "Płytarium API — wishlist, notifications, CSV, credentials, public routes",
+      "status": "pending"
+    },
+    {
+      "number": "14",
+      "name": "Domain jobs and external integrations",
+      "status": "pending"
+    },
+    {
+      "number": "15",
+      "name": "Cutover",
+      "status": "pending"
+    }
+  ],
+  "next": {
+    "command": "/gsd:progress --next",
+    "label": "Advance to the next step",
+    "reason": "Phase 09 of 15 · executing"
+  },
+  "updated_at": "2026-09-26T01:03:11.369Z"
+}