feat(T4): Railway deploy config + CI/CD

[openpango]

Summary

Complete Railway deployment setup for Queryx.

Deliverables

• Dockerfile — Bun runtime, health check, production-ready
• railway.json — Auto-restart on failure, health check path
• .env.example — All vars documented with descriptions
• DEPLOY.md — Zero-to-deployed guide (CLI + dashboard)
• Smoke test — Validates health + 402 on paid endpoints

CI Workflow (needs workflow scope to push)

Add .github/workflows/ci.yml:

name: CI
on:
  push: { branches: [main] }
  pull_request: { branches: [main] }
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: oven-sh/setup-bun@v2
      - run: bun install
      - run: bun test
      - run: bun run tsc --noEmit

Closes #4