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/routes.yaml

@@ -0,0 +1,22 @@
+apiVersion: configuration.konghq.com/v1alpha1
+kind: KongRoute
+metadata:
+  name: ${NAME}-payments-mcp
+  namespace: ${NAMESPACE}
+spec:
+  serviceRef:
+    type: namespacedRef
+    namespacedRef:
+      name: ${NAME}-payments-mcp
+  name: payments-mcp
+  hosts:
+    - ${REST_HOSTNAME}
+  methods:
+    - GET
+    - POST
+    - DELETE
+  paths:
+    - /payments-mcp
+  strip_path: false
+  tags:
+    - payments