feat: 后台管理功能增强

1. 前端用户下拉菜单优化 - 改用CSS动画，解决鼠标移动问题
2. 帖子管理增加显示/隐藏开关
3. 帖子详情页可直接删除回复
4. 新增回复管理页面（列表、删除）
5. 用户管理增加编辑功能（用户名、邮箱、手机、简介）
6. 用户管理增加查看帖子按钮
7. 所有页面侧边栏添加回复管理入口
8. 数据库增加 is_hidden 字段

models.py

@@ -54,6 +54,7 @@ class Database:
                     likes TEXT DEFAULT '[]',
                     views INTEGER DEFAULT 0,
                     is_pinned INTEGER DEFAULT 0,
+                    is_hidden INTEGER DEFAULT 0,
                     created_at TEXT,
                     updated_at TEXT,
                     FOREIGN KEY (author_id) REFERENCES users(id)
@@ -317,6 +318,24 @@ class ReplyModel:
                 reply['likes'] = json.loads(reply['likes'] or '[]')
                 replies.append(reply)
             return replies
+    
+    def delete(self, reply_id):
+        """删除回复"""
+        with self.db.get_conn() as conn:
+            conn.execute('DELETE FROM replies WHERE id = ?', (reply_id,))
+            conn.commit()
+            return True
+    
+    def get_all(self, limit=50):
+        """获取所有回复（后台管理用）"""
+        with self.db.get_conn() as conn:
+            rows = conn.execute('SELECT * FROM replies ORDER BY created_at DESC LIMIT ?', (limit,)).fetchall()
+            replies = []
+            for row in rows:
+                reply = dict(row)
+                reply['likes'] = json.loads(reply['likes'] or '[]')
+                replies.append(reply)
+            return replies
 
 
 class TopicModel: