Add Railway deployment configuration

- Add Dockerfiles for backend (FastAPI) and frontend (nginx)
- Add railway.toml configs with health checks
- Add .dockerignore files for optimized builds
- Update config.py to auto-convert Railway DATABASE_URL format
- Add FRONTEND_URL env var for production CORS

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/railway.toml

@@ -0,0 +1,9 @@
+[build]
+builder = "dockerfile"
+dockerfilePath = "Dockerfile"
+
+[deploy]
+healthcheckPath = "/health"
+healthcheckTimeout = 100
+restartPolicyType = "on_failure"
+restartPolicyMaxRetries = 3