refactor: 移除独立 hub/proxy/executor/gateway crate，统一为 gateway tunnel 架构

- 删除 aether-hub、aether-proxy 独立项目及其 Dockerfile/配置
- 删除 crates/aether-executor 和 crates/aether-gateway 全部模块
- 新增 apps/ 目录作为应用入口
- 将 hub 概念重构为 gateway tunnel transport
- 将 executor 重构为 execution runtime
- 新增 tunnel.rs 合约定义和 testkit tunnel/execution_runtime 模块
- 更新 Python 服务层和测试适配新架构命名

tests/unit/test_tunnel_config.py

@@ -0,0 +1,14 @@
+from src.services.proxy_node.tunnel_config import TunnelRelayConfig
+
+
+def test_local_relay_url_uses_http_path() -> None:
+    config = TunnelRelayConfig(
+        enabled=True,
+        url="http://127.0.0.1:8084",
+        connect_timeout_seconds=1.0,
+    )
+
+    assert (
+        config.local_relay_url("node a/1")
+        == "http://127.0.0.1:8084/api/internal/tunnel/relay/node%20a%2F1"
+    )