refactor(schemas): 统一 message/notification 命名边界，旧名收敛至兼容映射表

- notification 域：渠道能力（MessageChannel→NotificationChannel、ChannelCapability* 迁入 notification.py）
- message 域：消息收发（Notification→Message、NotificationType→MessageType、CommingMessage→IncomingMessage、NotificationHistoryItem→MessageHistoryItem、NotificationClear*→MessageClear*）
- Agent 工具契约：send_notification_message→send_message、notification_callback→message_callback
- 源码不保留旧名物理别名，旧导入经 app/runtime/compat/manifest.py SYMBOL_ALIASES 惰性解析
- API 路径与持久化键冻结不变，前端零改动
- 新增兼容守护测试与 docs/rules/07 命名边界规范

app/db/oper/message.py

@@ -6,7 +6,7 @@ from sqlalchemy.orm import Session
 
 from app.db import DbOper
 from app.db.models.message import Message
-from app.schemas import MessageChannel, NotificationType
+from app.schemas import NotificationChannel, MessageType
 
 
 class MessageOper(DbOper):
@@ -18,9 +18,9 @@ class MessageOper(DbOper):
         super().__init__(db)
 
     def add(self,
-            channel: Optional[MessageChannel] = None,
+            channel: Optional[NotificationChannel] = None,
             source: Optional[str] = None,
-            mtype: Optional[NotificationType] = None,
+            mtype: Optional[MessageType] = None,
             title: Optional[str] = None,
             text: Optional[str] = None,
             image: Optional[str] = None,
@@ -64,9 +64,9 @@ class MessageOper(DbOper):
         return Message(**kwargs).create_and_to_dict(self._db)
 
     async def async_add(self,
-                        channel: Optional[MessageChannel] = None,
+                        channel: Optional[NotificationChannel] = None,
                         source: Optional[str] = None,
-                        mtype: Optional[NotificationType] = None,
+                        mtype: Optional[MessageType] = None,
                         title: Optional[str] = None,
                         text: Optional[str] = None,
                         image: Optional[str] = None,