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, 12 insertions, 8 deletions

diff --git a/src/zencore/memory/memory.cpp b/src/zencore/memory/memory.cpp
index fc8de5d02..9e19c5db7 100644
--- a/src/zencore/memory/memory.cpp
+++ b/src/zencore/memory/memory.cpp
@@ -1,5 +1,7 @@
 // Copyright Epic Games, Inc. All Rights Reserved.
 
+#include <cstdlib>
+
 #include <zencore/commandline.h>
 #include <zencore/memory/fmalloc.h>
 #include <zencore/memory/mallocansi.h>
@@ -42,14 +44,6 @@ InitGMalloc()
 	// when using sanitizers, we should use the default/ansi allocator
 
 #if ZEN_OVERRIDE_NEW_DELETE
-
-#	if ZEN_MIMALLOC_ENABLED
-	if (Malloc == MallocImpl::None)
-	{
-		Malloc = MallocImpl::Mimalloc;
-	}
-#	endif
-
 #	if ZEN_RPMALLOC_ENABLED
 	if (Malloc == MallocImpl::None)
 	{
@@ -107,6 +101,16 @@ InitGMalloc()
 		}
 	};
 
+	// Check ZEN_MALLOC environment variable (overrides compile-time default, but not command line)
+	{
+		const char* EnvMalloc = getenv("ZEN_MALLOC");
+		if (EnvMalloc != nullptr)
+		{
+			ProcessMallocArg(std::string_view(EnvMalloc));
+		}
+	}
+
+	// Command line --malloc takes highest precedence
 	IterateCommandlineArgs(ProcessArg);
 
 	switch (Malloc)