HttpClient using libcurl, Unix Sockets for HTTP. HTTPS support (#770)

The main goal of this change is to eliminate the cpr back-end altogether and replace it with the curl implementation. I would expect to drop cpr as soon as we feel happy with the libcurl back-end. That would leave us with a direct dependency on libcurl only, and cpr can be eliminated as a dependency.

### HttpClient Backend Overhaul
- Implemented a new **libcurl-based HttpClient** backend (`httpclientcurl.cpp`, ~2000 lines)
  as an alternative to the cpr-based one
- Made HttpClient backend **configurable at runtime** via constructor arguments
  and `-httpclient=...` CLI option (for zen, zenserver, and tests)
- Extended HttpClient test suite to cover multipart/content-range scenarios

### Unix Domain Socket Support
- Added Unix domain socket support to **httpasio** (server side)
- Added Unix domain socket support to **HttpClient**
- Added Unix domain socket support to **HttpWsClient** (WebSocket client)
- Templatized `HttpServerConnectionT<SocketType>` and `WsAsioConnectionT<SocketType>`
  to handle TCP, Unix, and SSL sockets uniformly via `if constexpr` dispatch

### HTTPS Support
- Added **preliminary HTTPS support to httpasio** (for Mac/Linux via OpenSSL)
- Added **basic HTTPS support for http.sys** (Windows)
- Implemented HTTPS test for httpasio
- Split `InitializeServer` into smaller sub-functions for http.sys

### Other Notable Changes
- Improved **zenhttp-test stability** with dynamic port allocation
- Enhanced port retry logic in http.sys (handles ERROR_ACCESS_DENIED)
- Fatal signal/exception handlers for backtrace generation in tests
- Added `zen bench http` subcommand to exercise network + HTTP client/server communication stack

1 files changed, 2 insertions, 2 deletions

diff --git a/src/zenserver/sessions/sessions.cpp b/src/zenserver/sessions/sessions.cpp
index f73aa40ff..d919db6e9 100644
--- a/src/zenserver/sessions/sessions.cpp
+++ b/src/zenserver/sessions/sessions.cpp
@@ -64,6 +64,8 @@ SessionsService::RegisterSession(const Oid& SessionId, std::string AppName, cons
 		return false;
 	}
 
+	ZEN_INFO("Session {} registered (AppName: {}, JobId: {})", SessionId, AppName, JobId);
+
 	const DateTime Now = DateTime::Now();
 	m_Sessions.emplace(SessionId,
 					   Ref(new Session(SessionInfo{.Id		  = SessionId,
@@ -72,8 +74,6 @@ SessionsService::RegisterSession(const Oid& SessionId, std::string AppName, cons
 												   .Metadata  = CbObject::Clone(Metadata),
 												   .CreatedAt = Now,
 												   .UpdatedAt = Now})));
-
-	ZEN_INFO("Session {} registered (AppName: {}, JobId: {})", SessionId, AppName, JobId);
 	return true;
 }