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

tests/test_agent_image_capability.py

@@ -4,7 +4,7 @@ from app.agent import MoviePilotAgent
 from app.agent.llm import AgentCapabilityManager, LLMHelper
 from app.chain.message import MessageChain
 from app.runtime.config import settings
-from app.schemas.types import MessageChannel
+from app.schemas.types import NotificationChannel
 
 
 def test_llm_supports_image_input_uses_model_catalog_text_only(monkeypatch):
@@ -76,7 +76,7 @@ def test_handle_ai_message_routes_text_only_model_images_to_files(monkeypatch):
     ):
         chain._handle_ai_message(
             text="/ai 帮我看看这张图",
-            channel=MessageChannel.Telegram,
+            channel=NotificationChannel.Telegram,
             source="telegram-test",
             userid="10001",
             username="tester",