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.

api/src/index.ts

@@ -0,0 +1,21 @@
+import { Elysia } from "elysia";
+
+// Phase 0 skeleton: health check + a bare WS gateway endpoint that mod instances will
+// eventually authenticate against with a per-server token (see plan's "WS Gateway" module).
+// Delta/chat/link-request routing lands in Phase 1+.
+const app = new Elysia()
+  .get("/health", () => ({ status: "ok" }))
+  .ws("/ws", {
+    open(ws) {
+      console.log(`[ws] connection opened: ${ws.id}`);
+    },
+    message(ws, message) {
+      console.log(`[ws] message from ${ws.id}:`, message);
+    },
+    close(ws) {
+      console.log(`[ws] connection closed: ${ws.id}`);
+    },
+  })
+  .listen(Number(process.env.PORT ?? 3000));
+
+console.log(`[api] listening on :${app.server?.port}`);