build: portability groundwork toward a Windows/MSVC viewer

- CMakeLists.txt: fetch libzmq at the top level (zeromq/libzmq v4.3.5) before
  slsDetectorPackage, so this project controls the ZeroMQ version instead of sls's
  bundled archive. sls reuses it via its if(NOT libzmq_POPULATED) guard, so a single
  libzmq-static target is built (no duplicate-target/double-symbol clash). Verified the
  full Linux build still links (JFJochZMQ -> JFJochReceiver -> jfjoch_process).
- common/NetworkAddressConvert.cpp: guard the network includes for _WIN32
  (winsock2/ws2tcpip vs arpa/inet).
- common/ImageBuffer.cpp: use std::malloc/std::free for the non-NUMA path instead of an
  anonymous mmap (the mapping had no huge-page/mbind flags, so it was equivalent) -
  portable and removes the POSIX-only dependency. The NUMA-interleave path is unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

common/ImageBuffer.cpp

@@ -6,28 +6,27 @@
 #include "JFJochException.h"
 #include "ZeroCopyReturnValue.h"
 
+#include <cstdlib>
+
 #ifdef JFJOCH_USE_NUMA
 #include <numa.h>
 #endif
-#include <sys/mman.h>
 
 
 ImageBuffer::ImageBuffer(size_t buffer_size_bytes)
         : buffer_size(buffer_size_bytes) {
 
 #ifdef JFJOCH_USE_NUMA
+    // Interleave the buffer across NUMA nodes - throughput-critical path (receiver), Linux-only.
     buffer = static_cast<uint8_t *>(numa_alloc_interleaved(buffer_size));
+#else
+    // The non-NUMA mapping carried no huge-page / mbind flags, so a plain heap allocation is
+    // equivalent (and portable). The buffer is zeroed below.
+    buffer = static_cast<uint8_t *>(std::malloc(buffer_size));
+#endif
     if (buffer == nullptr)
-        throw JFJochException(JFJochExceptionCategory::MemAllocFailed,
-            "Failed to allocate image buffer");
-
-    #else
-    buffer = (uint8_t *) mmap (nullptr, buffer_size, PROT_READ | PROT_WRITE,
-                               MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) ;
-    if (buffer == MAP_FAILED)
         throw JFJochException(JFJochExceptionCategory::MemAllocFailed,
                               "Failed to allocate image buffer");
-#endif
     memset(buffer, 0, buffer_size);
 }
 
@@ -39,7 +38,7 @@ ImageBuffer::~ImageBuffer() {
 #ifdef JFJOCH_USE_NUMA
     numa_free(buffer, buffer_size);
 #else
-    munmap(buffer, buffer_size);
+    std::free(buffer);
 #endif
 }