chore: 添加虚拟环境到仓库

- 添加 backend_service/venv 虚拟环境
- 包含所有Python依赖包
- 注意：虚拟环境约393MB，包含12655个文件

backend_service/venv/lib/python3.13/site-packages/mcp/shared/message.py

@@ -0,0 +1,43 @@
+"""
+Message wrapper with metadata support.
+
+This module defines a wrapper type that combines JSONRPCMessage with metadata
+to support transport-specific features like resumability.
+"""
+
+from collections.abc import Awaitable, Callable
+from dataclasses import dataclass
+
+from mcp.types import JSONRPCMessage, RequestId
+
+ResumptionToken = str
+
+ResumptionTokenUpdateCallback = Callable[[ResumptionToken], Awaitable[None]]
+
+
+@dataclass
+class ClientMessageMetadata:
+    """Metadata specific to client messages."""
+
+    resumption_token: ResumptionToken | None = None
+    on_resumption_token_update: Callable[[ResumptionToken], Awaitable[None]] | None = None
+
+
+@dataclass
+class ServerMessageMetadata:
+    """Metadata specific to server messages."""
+
+    related_request_id: RequestId | None = None
+    # Request-specific context (e.g., headers, auth info)
+    request_context: object | None = None
+
+
+MessageMetadata = ClientMessageMetadata | ServerMessageMetadata | None
+
+
+@dataclass
+class SessionMessage:
+    """A message with specific metadata for transport-specific features."""
+
+    message: JSONRPCMessage
+    metadata: MessageMetadata = None