Phase 0: scaffold three-service backend (api/worker/frontend)

api/ (ElysiaJS+Bun WS gateway skeleton), worker/ (Rust, Redis dirty-chunk
stream consumer behind a swappable RenderBackend trait), frontend/
(ElysiaJS+Pug+Tailwind4+Alpine, one server-rendered page) — all three
verified running locally. docker-compose wires them up with postgres,
redis, minio (rendered tile/mesh object storage), and Caddy as reverse
proxy.

worker/.env.example

@@ -0,0 +1,8 @@
+DATABASE_URL=postgres://mcmapper:mcmapper@postgres:5432/mcmapper
+REDIS_URL=redis://redis:6379
+MINIO_ENDPOINT=minio
+MINIO_PORT=9000
+MINIO_ACCESS_KEY=mcmapper
+MINIO_SECRET_KEY=mcmapper-dev-only
+# cpu | gpu | hybrid — see render::backend. Only `cpu` exists so far (Phase 8 adds gpu/hybrid).
+RENDER_BACKEND=cpu