feat(F-091): completed feature

work/artifacts/F-091/reviewer.json

@@ -0,0 +1,13 @@
+{
+  "feature_id": "F-091",
+  "agent": "reviewer",
+  "verdict": "APPROVED",
+  "summary": "The API keeps SKU/EAN uniqueness, identifies the conflicting field from the database constraint, and the UI prevents duplicate in-flight saves while presenting actionable conflict feedback.",
+  "evidence": [
+    "Existing 409 uniqueness behavior is preserved",
+    "SKU and EAN constraint names map to field-specific domain messages",
+    "Enter plus blur is guarded by a per-field in-flight key",
+    "Root and admin typechecks pass"
+  ],
+  "timestamp": "2026-08-20T19:47:00Z"
+}