Add payments-mcp (Layer 3 MCP surface), single-route pattern from the start

list-payments/get-payment (all 5 roles) and create-payment (admin
only — matches PaymentPermission's actual write-access logic, not
guessed). One KongRoute for GET/POST/DELETE, one ai-mcp-proxy
binding — avoids the duplicate-tool-name bug found and fixed on
customers-mcp (STATUS.md section 18), built correctly here instead
of repeating the two-route mistake.

Keycloak (local): mcp-payments-audience client scope + mcp-payments
resource client, attached to librechat as an optional scope, no
dedicated protocol mappers on the client itself.

kong/mcp/service.yaml

@@ -0,0 +1,17 @@
+apiVersion: configuration.konghq.com/v1alpha1
+kind: KongService
+metadata:
+  name: ${NAME}-payments-mcp
+  namespace: ${NAMESPACE}
+spec:
+  controlPlaneRef:
+    type: konnectNamespacedRef
+    konnectNamespacedRef:
+      name: ${CONTROL_PLANE_REF_NAME}
+  name: payments-mcp
+  host: ${REST_HOSTNAME}
+  port: 80
+  protocol: http
+  path: /
+  tags:
+    - payments