feat(deploy): serve SPA from server, Dockerfile, compose, deploy docs

- Add serveStatic middleware to server/src/app.ts to serve web/dist
- Include SPA fallback route for client-side routing deep links
- Create Dockerfile with multi-stage build (Node deps + build, slim runtime)
- Add docker-compose.yml for single-command deployment
- Add docs/deploy.md with deployment instructions and Caddy reverse proxy example
- Add bun run build:web step to CI pipeline after typecheck

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docker-compose.yml

@@ -0,0 +1,8 @@
+services:
+  helios:
+    build: .
+    ports:
+      - "3000:3000"
+    volumes:
+      - ./data:/data
+    restart: unless-stopped