refactor(tunnel): 移除直连tunnel模式，统一使用Hub转发

- 删除 TunnelTransport 及 TunnelManager 相关引用，所有 tunnel 请求统一走 Hub
- 简化 health_scheduler，不再依赖进程内 TunnelManager 状态判断节点在线
- 简化 resolver，移除本地 tunnel miss 判断与多 worker 告警逻辑
- 简化 service 中 tunnel 连通性检测，统一以 DB 状态为准
- 启动/关闭流程移除 hub_enabled 分支，始终初始化 Hub 连接
- Rust 端 RequestMeta.timeout 增加浮点数反序列化支持，Python 端确保发送整数

tests/unit/test_tunnel_hub_factory.py

@@ -1,29 +1,9 @@
-import pytest
-
-from src.services.proxy_node.hub_config import reset_hub_config_cache
 from src.services.proxy_node.hub_transport import HubTunnelTransport
 from src.services.proxy_node.tunnel_protocol import Frame, MsgType
-from src.services.proxy_node.tunnel_transport import TunnelTransport, create_tunnel_transport
+from src.services.proxy_node.tunnel_transport import create_tunnel_transport
 
 
-def test_create_tunnel_transport_uses_legacy_transport_when_hub_disabled(
-    monkeypatch: pytest.MonkeyPatch,
-) -> None:
-    monkeypatch.setenv("DOCKER_CONTAINER", "false")
-    monkeypatch.setattr("src.services.proxy_node.hub_config.os.path.exists", lambda _: False)
-    reset_hub_config_cache()
-
-    transport = create_tunnel_transport("node-1", timeout=12.0)
-    assert isinstance(transport, TunnelTransport)
-
-
-def test_create_tunnel_transport_uses_hub_transport_when_hub_enabled(
-    monkeypatch: pytest.MonkeyPatch,
-) -> None:
-    monkeypatch.setenv("DOCKER_CONTAINER", "true")
-    monkeypatch.setattr("src.services.proxy_node.hub_config.os.path.exists", lambda _: False)
-    reset_hub_config_cache()
-
+def test_create_tunnel_transport_always_uses_hub_transport() -> None:
     transport = create_tunnel_transport("node-1", timeout=12.0)
     assert isinstance(transport, HubTunnelTransport)