fix: 多项修复

- main.py: 加 _CNJSONResponse 修复 datetime 序列化时区(+00:00→+08:00)
- schemas/__init__.py: 加 _fmt_dt 函数和 sync_to_platform 字段
- ai_service.py: 评论 max_tokens 从 300 提升到 500 避免截断
- scheduler.py: datetime.utcnow() 全部改为 datetime.now()（北京时间）
- docker-compose.yml: MySQL 容器加 TZ=Asia/Shanghai
- Interactions.vue: 文章标题链接从系统配置读取域名，格式为 {域名}/huihui-h5/#/news/share?id={id}&login=no

backend/app/services/ai_service.py

@@ -174,7 +174,7 @@ class AIService:
 5. 只输出评论正文，不要加任何前缀或解释
 
 评论："""
-        return await self._call_api(db, prompt, system_prompt, max_tokens=300)
+        return await self._call_api(db, prompt, system_prompt, max_tokens=500)
 
     async def generate_reply(
         self, db: AsyncSession, article_title: str, parent_comment: str,

backend/app/services/scheduler.py

@@ -146,7 +146,7 @@ class SchedulerService:
                 return
 
             # 检查互动间隔：过滤掉最近 min_interval 秒内已互动的用户
-            now_utc = datetime.utcnow()
+            now_utc = datetime.now()
             eligible = []
             for u in all_users:
                 if u.last_interact_at is None:
@@ -302,7 +302,7 @@ class SchedulerService:
                                 update(VirtualUser).where(VirtualUser.id == user_id).values(
                                     today_comment_count=VirtualUser.today_comment_count + 1,
                                     total_interactions=VirtualUser.total_interactions + 1,
-                                    last_interact_at=datetime.utcnow()
+                                    last_interact_at=datetime.now()
                                 )
                             )
 
@@ -342,7 +342,7 @@ class SchedulerService:
         await db.execute(
             update(VirtualUser).where(VirtualUser.id == user_id).values(
                 total_interactions=VirtualUser.total_interactions + 1,
-                last_interact_at=datetime.utcnow()
+                last_interact_at=datetime.now()
             )
         )