修复：PostgreSQL 语法适配 + UUID 自动生成

backend/app/db/init_db.py

@@ -34,16 +34,14 @@ async def _create_contacts_table(conn):
             email VARCHAR(100),
             company VARCHAR(100),
             position VARCHAR(100),
-            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
-            
-            INDEX idx_contacts_user (user_id)
+            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
         );
     """
     
     try:
         async with conn.cursor() as cur:
             await cur.execute(sql)
-            # 注释掉 INFO 打印，避免噪声
+            await _create_index_if_not_exists(conn, "idx_contacts_user", "contacts", "user_id")
     except Exception as e:
         print(f"contacts 表可能已存在: {e}")
 
@@ -59,16 +57,15 @@ async def _create_words_table(conn):
             part_of_speech VARCHAR(50),
             definition TEXT,
             examples TEXT,
-            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
-            
-            INDEX idx_words_user (user_id),
-            INDEX idx_words_word (word)
+            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
         );
     """
     
     try:
         async with conn.cursor() as cur:
             await cur.execute(sql)
+            await _create_index_if_not_exists(conn, "idx_words_user", "words", "user_id")
+            await _create_index_if_not_exists(conn, "idx_words_word", "words", "word")
     except Exception as e:
         print(f"words 表可能已存在: {e}")
 
@@ -84,14 +81,23 @@ async def _create_news_table(conn):
             url VARCHAR(500),
             source VARCHAR(100),
             keywords TEXT,
-            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
-            
-            INDEX idx_news_user (user_id)
+            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
         );
     """
     
     try:
         async with conn.cursor() as cur:
             await cur.execute(sql)
+            await _create_index_if_not_exists(conn, "idx_news_user", "news", "user_id")
     except Exception as e:
         print(f"news 表可能已存在: {e}")
+
+
+async def _create_index_if_not_exists(conn, index_name: str, table_name: str, column_name: str):
+    """创建索引（如果不存在）"""
+    sql = f"CREATE INDEX IF NOT EXISTS {index_name} ON {table_name} ({column_name});"
+    try:
+        async with conn.cursor() as cur:
+            await cur.execute(sql)
+    except Exception as e:
+        print(f"索引 {index_name} 可能已存在: {e}")