feat: add /history and /search commands

- Add /history [N] command to view recent conversation history
  - Default 20 messages, max 100
  - Shows date/time, role (user/bot), and message preview
- Add /search <keyword> command to search conversations
  - Uses extractKeywords() for smart keyword extraction
  - Shows up to 15 results with date and content preview
- Update /stats command to use new conversation-storage service
  - Shows total message count, first/last message dates
  - Shows archived summary count
  - Links to /history and /search commands
- Update /start and /help commands to include new commands
- Import conversation-storage functions

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

src/commands.ts

@@ -1,5 +1,11 @@
 import { Env } from './types';
 import { getConversationContext, getLatestSummary } from './summary-service';
+import {
+  getConversationHistory,
+  searchConversations,
+  getConversationStats,
+  extractKeywords
+} from './services/conversation-storage';
 
 export async function handleCommand(
   env: Env,
@@ -26,6 +32,8 @@ export async function handleCommand(
 /server - 내 서버 목록
 /security - DDoS 방어 현황
 /phantomx - PhantomX VPN
+/history - 대화 기록
+/search - 대화 검색
 
 무엇을 도와드릴까요?`;
 
@@ -38,6 +46,8 @@ export async function handleCommand(
 /server - 내 서버 목록
 /security - DDoS 방어 서비스
 /phantomx - PhantomX VPN 서비스
+/history [N] - 대화 기록 (기본 20개)
+/search 키워드 - 대화 검색
 
 <b>자연어로 요청:</b>
 • "도메인 등록" - 도메인 검색/등록
@@ -90,19 +100,88 @@ ${summary.summary}
 <i>업데이트: ${createdAt}</i>`;
     }
 
+    case '/history': {
+      const limit = _args ? parseInt(_args, 10) : 20;
+      const validLimit = Math.min(Math.max(limit, 1), 100); // 1-100 제한
+
+      const messages = await getConversationHistory(env.DB, chatId, validLimit);
+
+      if (messages.length === 0) {
+        return '📜 저장된 대화가 없습니다.';
+      }
+
+      const formatted = messages.map(m => {
+        const time = m.created_at
+          ? new Date(m.created_at).toLocaleString('ko-KR', {
+              timeZone: 'Asia/Seoul',
+              month: '2-digit',
+              day: '2-digit',
+              hour: '2-digit',
+              minute: '2-digit'
+            })
+          : '';
+        const role = m.role === 'user' ? '나' : '봇';
+        const content = m.content.length > 50
+          ? m.content.substring(0, 50) + '...'
+          : m.content;
+        return `[${time}] ${role}: ${content}`;
+      }).join('\n');
+
+      return `📜 <b>최근 대화</b> (${messages.length}개)\n\n${formatted}\n\n/history 50 으로 더 보기`;
+    }
+
+    case '/search': {
+      if (!_args || _args.trim().length < 2) {
+        return '🔍 검색어를 입력해주세요.\n예: /search 도메인';
+      }
+
+      const keywords = extractKeywords(_args);
+      if (keywords.length === 0) {
+        return '🔍 유효한 검색어가 없습니다.';
+      }
+
+      const results = await searchConversations(env.DB, chatId, keywords, 15);
+
+      if (results.length === 0) {
+        return `🔍 "${_args}" 검색 결과가 없습니다.`;
+      }
+
+      const formatted = results.map(m => {
+        const date = m.created_at
+          ? new Date(m.created_at).toLocaleDateString('ko-KR')
+          : '';
+        const content = m.content.length > 60
+          ? m.content.substring(0, 60) + '...'
+          : m.content;
+        return `[${date}] ${content}`;
+      }).join('\n');
+
+      return `🔍 <b>"${_args}"</b> 검색 결과 (${results.length}건)\n\n${formatted}`;
+    }
+
     case '/stats': {
-      const ctx = await getConversationContext(env.DB, userId, chatId);
-      const profileCount = await env.DB
-        .prepare('SELECT COUNT(*) as cnt FROM summaries WHERE user_id = ?')
-        .bind(userId)
-        .first<{ cnt: number }>();
+      const stats = await getConversationStats(env.DB, chatId);
+
+      if (!stats) {
+        return '📈 아직 대화 기록이 없습니다.';
+      }
+
+      const firstDate = stats.first_message_at
+        ? new Date(stats.first_message_at).toLocaleDateString('ko-KR')
+        : '없음';
+      const lastDate = stats.last_message_at
+        ? new Date(stats.last_message_at).toLocaleDateString('ko-KR')
+        : '없음';
 
       return `📈 <b>대화 통계</b>
 
-총 메시지: ${ctx.totalMessages}개
-프로필 버전: ${ctx.previousSummary?.generation ?? 0}
-저장된 프로필: ${profileCount?.cnt ?? 0}개
-버퍼 대기: ${ctx.recentMessages.length}개`;
+총 메시지: ${stats.message_count.toLocaleString()}개
+첫 대화: ${firstDate}
+최근 대화: ${lastDate}
+아카이브된 요약: ${stats.archived_summaries}개
+
+/history - 대화 기록 보기
+/search 키워드 - 대화 검색`;
     }
 
     case '/domain': {