feat: X 봇 프로필 정보 DB 저장 기능 추가

- x_profiles 테이블 생성 (username, display_name, avatar_url)
- saveProfile 함수로 DB + Redis 캐시 동시 저장
- getProfile 함수 Redis → DB 폴백 지원

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

backend/sql/x_profiles.sql

@@ -0,0 +1,10 @@
+-- X 프로필 테이블
+CREATE TABLE IF NOT EXISTS x_profiles (
+    id INT AUTO_INCREMENT PRIMARY KEY,
+    username VARCHAR(50) NOT NULL UNIQUE,
+    display_name VARCHAR(100),
+    avatar_url TEXT,
+    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+    INDEX idx_username (username)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

backend/src/services/x/index.js

@@ -20,11 +20,22 @@ async function xBotPlugin(fastify, opts) {
   }
 
   /**
-   * X 프로필 캐시 저장
+   * X 프로필 저장 (DB + Redis 캐시)
    */
-  async function cacheProfile(username, profile) {
+  async function saveProfile(username, profile) {
     if (!profile.displayName && !profile.avatarUrl) return;
 
+    // DB에 저장 (upsert)
+    await fastify.db.query(`
+      INSERT INTO x_profiles (username, display_name, avatar_url)
+      VALUES (?, ?, ?)
+      ON DUPLICATE KEY UPDATE
+        display_name = VALUES(display_name),
+        avatar_url = VALUES(avatar_url),
+        updated_at = CURRENT_TIMESTAMP
+    `, [username, profile.displayName, profile.avatarUrl]);
+
+    // Redis 캐시에도 저장
     const data = {
       username,
       displayName: profile.displayName,
@@ -139,8 +150,8 @@ async function xBotPlugin(fastify, opts) {
   async function syncNewTweets(bot) {
     const { tweets, profile } = await fetchTweets(bot.nitterUrl, bot.username);
 
-    // 프로필 캐시 업데이트
-    await cacheProfile(bot.username, profile);
+    // 프로필 저장 (DB + 캐시)
+    await saveProfile(bot.username, profile);
 
     let addedCount = 0;
     let ytAddedCount = 0;
@@ -178,11 +189,39 @@ async function xBotPlugin(fastify, opts) {
   }
 
   /**
-   * X 프로필 조회
+   * X 프로필 조회 (Redis 캐시 → DB)
    */
   async function getProfile(username) {
-    const data = await fastify.redis.get(`${PROFILE_CACHE_PREFIX}${username}`);
-    return data ? JSON.parse(data) : null;
+    // Redis 캐시 확인
+    const cached = await fastify.redis.get(`${PROFILE_CACHE_PREFIX}${username}`);
+    if (cached) {
+      return JSON.parse(cached);
+    }
+
+    // DB에서 조회
+    const [rows] = await fastify.db.query(
+      'SELECT username, display_name, avatar_url, updated_at FROM x_profiles WHERE username = ?',
+      [username]
+    );
+
+    if (rows.length > 0) {
+      const row = rows[0];
+      const data = {
+        username: row.username,
+        displayName: row.display_name,
+        avatarUrl: row.avatar_url,
+        updatedAt: row.updated_at?.toISOString(),
+      };
+      // Redis 캐시에 저장
+      await fastify.redis.setex(
+        `${PROFILE_CACHE_PREFIX}${username}`,
+        PROFILE_TTL,
+        JSON.stringify(data)
+      );
+      return data;
+    }
+
+    return null;
   }
 
   fastify.decorate('xBot', {