Fix three Windows-specific compile errors

- logger.cpp: use localtime_s on Windows (reversed arg order vs localtime_r)
- process.hpp: drop constexpr on INVALID_PROCESS (INVALID_HANDLE_VALUE is a
  reinterpret_cast, not valid in constexpr context)
- world_packets.hpp: push/pop ERROR macro around CharCreateResult enum to avoid
  clash with wingdi.h #define ERROR 0

src/core/logger.cpp

@@ -35,7 +35,11 @@ void Logger::log(LogLevel level, const std::string& message) {
         now.time_since_epoch()) % 1000;
 
     std::tm tm;
+#ifdef _WIN32
+    localtime_s(&tm, &time);
+#else
     localtime_r(&time, &tm);
+#endif
 
     // Format: [YYYY-MM-DD HH:MM:SS.mmm] [LEVEL] message
     std::ostringstream line;