docs+fix: update arch diagram/README/Insomnia, ApiError returns JSON

- architecture.mmd: CQRS trait names, ImageFetcher/RssFeedRenderer
  ports, infra-wiring crate, api-types description
- README: add infra-wiring, note CQRS ports
- Insomnia: add PATCH /api/v1/reviews/:id
- ApiError returns {"error":"..."} JSON not plain text

crates/presentation/src/errors.rs

@@ -36,6 +36,13 @@ impl From<DomainError> for ApiError {
 
 impl IntoResponse for ApiError {
     fn into_response(self) -> Response {
-        domain_error_response(self.0)
+        let status = domain_error_status(&self.0);
+        match &self.0 {
+            DomainError::InfrastructureError(_) => {
+                tracing::error!("Internal error: {:?}", self.0);
+                (status, axum::Json(serde_json::json!({"error": "internal server error"}))).into_response()
+            }
+            _ => (status, axum::Json(serde_json::json!({"error": self.0.to_string()}))).into_response(),
+        }
     }
 }