fix(mcp): HTTP 模式新增 --allowed-hosts，修 LAN Host 421

Windows 实测：绑 0.0.0.0 后局域网请求被 mcp DNS 重绑定防护 421 拒。
- parse_args 加 --allowed-hosts（逗号分隔 Host 白名单，默认 None 保持
  mcp 仅 localhost 族行为）
- build_server(manager, allowed_hosts=...) 经 TransportSecuritySettings
  传入（mcp 1.29.0 API 与设计一致，无需调整）
- main() 逗号拆分（去空白、丢空段）
- 回归测试：TestClient 驱动真实 ASGI app（含 lifespan），
  Host=192.168.61.35:8972 initialize → 200；Host=evil.example.com → 421

Co-Authored-By: Claude <noreply@anthropic.com>

tests/test_mcp_server.py

@@ -1,4 +1,4 @@
-"""mcp_server 测试：参数解析 + 非回环强制 token + ASGI 鉴权中间件。"""
+"""mcp_server 测试：参数解析 + 非回环强制 token + ASGI 鉴权中间件 + HTTP Host 白名单。"""
 import asyncio
 
 import pytest
@@ -25,6 +25,13 @@ class TestParseArgs:
         assert a.port == 9000 and a.mac == "AA:BB:CC:DD:EE:FF"
         assert a.connect_timeout == 120.0 and a.idle_timeout == 60.0
 
+    def test_allowed_hosts_default_none(self):
+        assert parse_args([]).allowed_hosts is None
+
+    def test_allowed_hosts_flag(self):
+        a = parse_args(["--allowed-hosts", "192.168.61.35:8972,localhost:8972"])
+        assert a.allowed_hosts == "192.168.61.35:8972,localhost:8972"
+
 
 def run_middleware(token_set, auth_header):
     """驱动 TokenAuthMiddleware，返回 (status, app_called)。"""
@@ -70,3 +77,45 @@ class TestBindGuard:
         monkeypatch.delenv(TOKEN_ENV, raising=False)
         with pytest.raises(SystemExit):
             main(["--transport", "http", "--host", "0.0.0.0"])
+
+
+class TestAllowedHosts:
+    """HTTP 模式 Host 白名单回归（Windows 实测：LAN Host 被 421 拒）。
+
+    用 starlette TestClient 驱动真实 ASGI app（含 lifespan，stateless 会话管理器
+    需要其 task group）；manager 只构造不连接，initialize 不触达设备。
+    """
+
+    LAN_HOST = "192.168.61.35:8972"
+
+    def _make_app(self):
+        from ppclock.device_manager import DeviceManager
+        from ppclock.mcp_server import build_server
+        manager = DeviceManager(mac="AA:BB:CC:DD:EE:FF")
+        mcp = build_server(manager, allowed_hosts=[self.LAN_HOST,
+                                                   "localhost:8972"])
+        return mcp.streamable_http_app()
+
+    def _initialize(self, app, host):
+        from starlette.testclient import TestClient
+        with TestClient(app) as client:
+            return client.post(
+                "/mcp",
+                headers={
+                    "Host": host,
+                    "Accept": "application/json, text/event-stream",
+                    "Content-Type": "application/json",
+                },
+                json={"jsonrpc": "2.0", "id": 1, "method": "initialize",
+                      "params": {"protocolVersion": "2025-03-26",
+                                 "capabilities": {},
+                                 "clientInfo": {"name": "test", "version": "0"}}},
+            )
+
+    def test_lan_host_not_421(self):
+        r = self._initialize(self._make_app(), self.LAN_HOST)
+        assert r.status_code != 421
+
+    def test_evil_host_421(self):
+        r = self._initialize(self._make_app(), "evil.example.com")
+        assert r.status_code == 421