修复内容库分页：返回总数而非当前页数量

- 新增 get_articles_count 函数获取总数
- 列表API返回总数用于分页计算

models/database.py

@@ -198,6 +198,14 @@ class Database:
             cursor.execute('DELETE FROM articles WHERE id = ?', (article_id,))
             conn.commit()
             return cursor.rowcount > 0
+    
+    def get_articles_count(self):
+        """获取文章总数"""
+        with self.get_connection() as conn:
+            cursor = conn.cursor()
+            cursor.execute('SELECT COUNT(*) as count FROM articles')
+            row = cursor.fetchone()
+            return row['count'] if row else 0
 
 # ========== 待处理产品操作 ==========
     def add_pending_product(self, product_name, category=None, subcategory=None, priority=0, source='manual'):