Add Railway deployment manifest for Dockerfile-based runtime

[Copilot]

This updates the repository to include an explicit Railway deployment manifest aligned with the intended infrastructure settings. It defines Dockerfile-based builds and stable single-replica deployment behavior with bounded restart retries.

• Deployment manifest

  • Added railway.json at repo root using Railway schema.
  • Declares DOCKERFILE builder with dockerfilePath: "/Dockerfile" and buildEnvironment: "V3".

• Runtime and resilience policy

  • Configures runtime V2, numReplicas: 1, and sleepApplication: false.
  • Sets restart policy to ON_FAILURE with restartPolicyMaxRetries: 10.

• Region and network settings

  • Enables multi-region config with sfo set to one replica.
  • Keeps ipv6EgressEnabled: false and useLegacyStacker: false.

{
  "$schema": "https://railway.com/railway.schema.json",
  "build": {
    "builder": "DOCKERFILE",
    "dockerfilePath": "/Dockerfile",
    "buildEnvironment": "V3"
  },
  "deploy": {
    "runtime": "V2",
    "numReplicas": 1,
    "multiRegionConfig": { "sfo": { "numReplicas": 1 } },
    "restartPolicyType": "ON_FAILURE",
    "restartPolicyMaxRetries": 10
  }
}