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/startup/modules_initializer.py

@@ -33,7 +33,7 @@ from app.adapters.external.server import MoviePilotServerHelper
 from app.db import close_database
 from app.db.oper.systemconfig import SystemConfigOper
 from app.command import CommandChain
-from app.schemas import Notification, NotificationType
+from app.schemas import Message, MessageType
 from app.schemas.types import SystemConfigKey
 from app.startup.agent_initializer import init_agent, stop_agent
 from app.application.security.access import set_superuser_token_payload_provider
@@ -148,8 +148,8 @@ def check_auth():
         err_msg = "用户认证失败，站点相关功能将无法使用！"
         MessageHelper().put(f"注意：{err_msg}", title="用户认证", role="system")
         CommandChain().post_message(
-            Notification(
-                mtype=NotificationType.Manual,
+            Message(
+                mtype=MessageType.Manual,
                 title="MoviePilot用户认证",
                 text=err_msg,
                 link=settings.MP_DOMAIN('#/site')