fix(chat,docker): return 503 for rate-limited providers and bundle node-machine-id

- chat: always return 503 Service Unavailable when all credentials are rate-limited
- Dockerfile: explicitly copy node-machine-id into standalone runtime image

src/sse/handlers/chat.js

@@ -237,7 +237,7 @@ async function handleSingleModelChat(body, modelStr, clientRawRequest = null, re
     if (!credentials || credentials.allRateLimited) {
       if (credentials?.allRateLimited) {
         const errorMsg = lastError || credentials.lastError || "Unavailable";
-        const status = lastStatus || Number(credentials.lastErrorCode) || HTTP_STATUS.SERVICE_UNAVAILABLE;
+        const status = HTTP_STATUS.SERVICE_UNAVAILABLE;
         log.warn("CHAT", `[${provider}/${model}] ${errorMsg} (${credentials.retryAfterHuman})`);
         return unavailableResponse(status, `[${provider}/${model}] ${errorMsg}`, credentials.retryAfter, credentials.retryAfterHuman);
       }