fix: server recommendation issues and __DIRECT__ tag visibility

- Fix USD price display: all prices now show in KRW (₩)
- Add Korea region auto-detection: extracts region preference from user messages
- Fix low-spec recommendation for high-performance requirements:
  - Add extractTechStack() to detect PostgreSQL, Redis, MongoDB keywords
  - Enhance inferExpectedUsers() to consider tech stack complexity
  - SaaS/B2B services now recommend 4GB+ RAM servers
- Fix __DIRECT__ tag appearing in output:
  - Reorder message concatenation in server-agent.ts
  - Add stripping logic in conversation-service.ts and api.ts

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/services/conversation-service.ts

@@ -5,6 +5,9 @@ import {
   generateAIResponse,
 } from '../summary-service';
 import { sendChatAction } from '../telegram';
+import { createLogger } from '../utils/logger';
+
+const logger = createLogger('conversation');
 
 export interface ConversationResult {
   responseText: string;
@@ -26,7 +29,9 @@ export class ConversationService {
     telegramUserId: string
   ): Promise<ConversationResult> {
     // 1. 타이핑 액션 전송 (비동기로 실행, 기다리지 않음)
-    sendChatAction(this.env.BOT_TOKEN, Number(chatId), 'typing').catch(console.error);
+    sendChatAction(this.env.BOT_TOKEN, Number(chatId), 'typing').catch(err =>
+      logger.error('타이핑 액션 전송 실패', err as Error)
+    );
 
     // 2. 사용자 메시지 버퍼에 추가
     await addToBuffer(this.env.DB, userId, chatId, 'user', text);
@@ -40,6 +45,12 @@ export class ConversationService {
       telegramUserId
     );
 
+    // __DIRECT__ 마커 제거 (AI가 그대로 전달한 경우 대비)
+    if (responseText.includes('__DIRECT__')) {
+      const directIndex = responseText.indexOf('__DIRECT__');
+      responseText = responseText.slice(directIndex + '__DIRECT__'.length).trim();
+    }
+
     // 4. 봇 응답 버퍼에 추가 (키보드 데이터 마커 등은 그대로 저장)
     // 실제 사용자에게 보여질 텍스트만 저장하는 것이 좋으나, 
     // 현재 구조상 전체를 저장하고 나중에 컨텍스트로 활용 시 정제될 수 있음
@@ -58,18 +69,18 @@ export class ConversationService {
     const keyboardMatch = responseText.match(/__KEYBOARD__(.+?)__END__\n?/s);
 
     if (keyboardMatch) {
-      console.log('[ConversationService] Keyboard marker detected:', keyboardMatch[1].substring(0, 100));
+      logger.debug('키보드 마커 감지', { preview: keyboardMatch[1].substring(0, 100) });
       responseText = responseText.replace(/__KEYBOARD__.+?__END__\n?/s, '');
       try {
         keyboardData = JSON.parse(keyboardMatch[1]) as KeyboardData;
-        console.log('[ConversationService] Keyboard parsed successfully:', keyboardData.type);
+        logger.debug('키보드 파싱 성공', { type: keyboardData.type });
       } catch (e) {
-        console.error('[ConversationService] Keyboard parsing error:', e);
-        console.error('[ConversationService] Failed to parse:', keyboardMatch[1]);
+        logger.error('키보드 파싱 오류', e as Error, { rawData: keyboardMatch[1] });
       }
     } else if (responseText.includes('__KEYBOARD__')) {
-      console.warn('[ConversationService] Keyboard marker found but regex did not match');
-      console.warn('[ConversationService] Response preview:', responseText.substring(0, 200));
+      logger.warn('키보드 마커 발견했으나 정규식 매칭 실패', {
+        preview: responseText.substring(0, 200)
+      });
     }
 
     return {