Bump to v1.13.1 - fix /health/ready res.status bug

The readiness probe was using asyncHandler directly, but this codebase's
asyncHandler has signature (logError, fn, context) — first arg is the logger.
Switched to boundAsyncHandler which is what every other route in src/app.js
uses. Verified working on both DNS2 (Docker) and Contabo (systemd).

8 new tests in __tests__/health-endpoints.test.js verify both endpoints.

dashcaddy-api/package.json

@@ -1,6 +1,6 @@
 {
   "name": "dashcaddy-api",
-  "version": "1.13.0",
+  "version": "1.13.1",
   "description": "DashCaddy API server - Dashboard backend for Docker, Caddy & DNS management",
   "main": "server.js",
   "scripts": {