Add guidance message for non-customers before onboarding redirect

Non-customers attempting to use customer-only features (troubleshoot,
billing, asset) now see a friendly explanation before being handed off
to the onboarding agent.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/i18n/en.ts

@@ -5,6 +5,7 @@ const en: Record<string, string> = {
   error_rate_limit: 'Too many requests. Please try again later.',
   error_blocked: 'Your account has been restricted.',
   error_ai_unavailable: 'AI service is temporarily unstable. Please try again later.',
+  error_customer_only: 'This feature is available to active customers only. I can help you with service registration or pricing information.',
   feedback_prompt: 'Was this consultation helpful?',
   feedback_thanks: 'Thank you for your feedback!',
   session_end: 'The consultation has ended. Feel free to reach out anytime for further inquiries.',

src/i18n/ko.ts

@@ -5,6 +5,7 @@ const ko: Record<string, string> = {
   error_rate_limit: '요청이 너무 많습니다. 잠시 후 다시 시도해주세요.',
   error_blocked: '이용이 제한된 계정입니다.',
   error_ai_unavailable: 'AI 서비스가 일시적으로 불안정합니다. 잠시 후 다시 시도해주세요.',
+  error_customer_only: '해당 기능은 서비스 이용 고객 전용입니다. 서비스 가입이나 요금 안내를 도와드리겠습니다.',
   feedback_prompt: '상담이 도움이 되셨나요?',
   feedback_thanks: '피드백 감사합니다!',
   session_end: '상담이 종료되었습니다. 추가 문의가 있으시면 언제든 말씀해주세요.',

src/routes/handlers/message-handler.ts

@@ -103,6 +103,10 @@ export async function handleMessage(
       const isCustomer = await checkIsCustomer(env.DB, telegramUserId);
       if (!isCustomer) {
         logger.info('비고객 → 온보딩 전환', { intent, telegramUserId });
+        await sendMessage(
+          env.BOT_TOKEN, chatId,
+          getMessage(lang, 'error_customer_only')
+        );
         const response = await onboardingAgent.processConsultation(env.DB, telegramUserId, text, env, meta);
         const { cleanText, sessionEnded } = cleanSessionMarkers(response);
         await storeConversation(env.DB, user.id, text, cleanText, requestId);