feat(bff): relay refused diplomas as 422 with reason, scanner down as 503 (refs #192)

openapi.json and the generated portal client regenerated from the served spec.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

services/bff/openapi.json

@@ -124,6 +124,19 @@
           },
           "404": {
             "description": "Not Found"
+          },
+          "422": {
+            "description": "Unprocessable Entity",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/Refusal"
+                }
+              }
+            }
+          },
+          "503": {
+            "description": "Service Unavailable"
           }
         }
       }
@@ -415,6 +428,17 @@
           }
         }
       },
+      "Refusal": {
+        "required": [
+          "reason"
+        ],
+        "type": "object",
+        "properties": {
+          "reason": {
+            "type": "string"
+          }
+        }
+      },
       "SubmitAccepted": {
         "required": [
           "registrationId",