fix: Railway deployment config — use root healthcheck, explicit start command

- Revert healthcheck to root path (always returns 200)
- Explicit startCommand for Nixpacks
- Railway will auto-detect from GitHub push

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

Author: ralyodio

railway.json

@@ -7,7 +7,8 @@
     "numReplicas": 1,
     "restartPolicyType": "ON_FAILURE",
     "restartPolicyMaxRetries": 10,
-    "healthcheckPath": "/api/health",
-    "healthcheckTimeout": 300
+    "healthcheckPath": "/",
+    "healthcheckTimeout": 300,
+    "startCommand": "node .next/standalone/server.js"
   }
 }