feat: add Railway deployment configs, docs, and demo improvements

[gitteri]

Summary

• Railway deployment guide (docs/RAILWAY.md) -- 390-line comprehensive guide covering service setup, environment variables, networking, and troubleshooting for deploying the full Contra stack on Railway.
• Railway-specific configs for indexer and operator services (indexer/config/railway/) -- 4 TOML config files tuned for Railway's environment.
• Dockerfile updates -- adds the streamer binary to the production image, copies indexer config files to /etc/contra/config, resolves the withdraw program .so symlink during build, and removes the VOLUME directive (incompatible with Railway).
• Docker Compose -- adds the streamer service with proper database dependencies and environment variables.
• Demo app improvements -- adds Vite proxy configuration for read/write RPC routing, improves load test hook with better error handling and configurable parameters.

Changed files

• docs/RAILWAY.md
• indexer/config/railway/indexer-contra.toml, indexer-solana.toml, operator-contra.toml, operator-solana.toml
• Dockerfile
• docker-compose.yml
• demo/src/hooks/useLoadTest.ts, demo/src/utils/solana.ts, demo/vite.config.ts

Dependencies

• Requires #5 feat/ws-streamer to be merged first (base branch) since Dockerfile and docker-compose reference the streamer binary.

Test plan

• docker build . succeeds with streamer binary included
• docker compose up streamer starts and connects to databases
• Railway config files are valid TOML and contain correct environment variable references
• Demo app pnpm dev starts with proxy working for /api/read and /api/write
• Demo load test runs with improved error handling

Made with Cursor