Transparent proxy mode (#823)

Adds a **transparent TCP proxy mode** to zenserver (activated via `zenserver proxy`), allowing it to sit between clients and upstream Zen servers to inspect and monitor HTTP/1.x traffic in real time. Primarily useful during development, to be able to observe multi-server/client interactions in one place.

- **Dedicated proxy port** -- Proxy mode defaults to port 8118 with its own data directory to avoid collisions with a normal zenserver instance.
- **TCP proxy core** (`src/zenserver/proxy/`) -- A new transparent TCP proxy that forwards connections to upstream targets, with support for both TCP/IP and Unix socket listeners. Multi-threaded I/O for connection handling. Supports Unix domain sockets for both upstream/downstream.
- **HTTP traffic inspection** -- Parses HTTP/1.x request/response streams inline to extract method, path, status, content length, and WebSocket upgrades without breaking the proxied data.
- **Proxy dashboard** -- A web UI showing live connection stats, per-target request counts, active connections, bytes transferred, and client IP/session ID rollups.
- **Server mode display** -- Dashboard banner now shows the running server mode (Zen Proxy, Zen Compute, etc.).

Supporting changes included in this branch:

- **Wildcard log level matching** -- Log levels can now be set per-category using wildcard patterns (e.g. `proxy.*=debug`).
- **`zen down --all`** -- New flag to shut down all running zenserver instances; also used by the new `xmake kill` task.
- Minor test stability fixes (flaky hash collisions, per-thread RNG seeds).
- Support ZEN_MALLOC environment variable for default allocator selection and switch default to rpmalloc
- Fixed sentry-native build to allow LTO on Windows

1 files changed, 39 insertions, 0 deletions

diff --git a/src/zenserver/proxy/httpproxystats.h b/src/zenserver/proxy/httpproxystats.h
new file mode 100644
index 000000000..76ac7c875
--- /dev/null
+++ b/src/zenserver/proxy/httpproxystats.h
@@ -0,0 +1,39 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#pragma once
+
+#include <zenhttp/httpserver.h>
+
+#include <memory>
+#include <vector>
+
+namespace zen {
+
+class TcpProxyService;
+
+class HttpProxyStatsService : public HttpService, public IHttpStatsProvider
+{
+public:
+	HttpProxyStatsService(const std::vector<std::unique_ptr<TcpProxyService>>& ProxyServices,
+						  IHttpStatsService&								   StatsService,
+						  std::string										   DefaultRecordDir);
+	~HttpProxyStatsService();
+
+	virtual const char* BaseUri() const override;
+	virtual void		HandleRequest(HttpServerRequest& Request) override;
+
+	// IHttpStatsProvider
+	virtual void	 HandleStatsRequest(HttpServerRequest& Request) override;
+	virtual CbObject CollectStats() override;
+
+private:
+	void HandleRecordStart(HttpServerRequest& Request);
+	void HandleRecordStop(HttpServerRequest& Request);
+	void HandleRecordStatus(HttpServerRequest& Request);
+
+	const std::vector<std::unique_ptr<TcpProxyService>>& m_ProxyServices;
+	IHttpStatsService&									 m_StatsService;
+	std::string											 m_DefaultRecordDir;
+};
+
+}  // namespace zen