Strip dead Windows-only code paths, add LTO/march build flags, seed default GM account

Removes now-unreachable #ifdef _WIN32 branches across Common/ and the three
server binaries (all builds are Linux-only), deletes the entirely unused
SEH exception-handling shim and an orphaned vendored MySQL client header.
Enables LTO and -march=x86-64-v2 in Release builds for a small free perf win.

Also seeds a default GM account (gmadmin/changeme) via
database sql files/gm_account.sql so a fresh deploy has something to log
into the web admin panel with, switches the MariaDB data directory from a
Docker named volume to a host bind mount for visibility/backup, and expands
the README with a fuller Docker deployment walkthrough.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Src/Common/SocketBase.cpp

@@ -45,23 +45,14 @@ void CBaseSocket::CloseSocket( void )
 	isActive	= false;
 }
 
-// Init winsocket, if we are using Windows
+// No-op on Linux; kept so call sites don't need to special-case platforms.
 bool InitWinSocket ( void )
 {
-#ifdef _WIN32
-	WSADATA wsa;
-	return (WSAStartup(MAKEWORD(2,0),&wsa)==0);
-#else
 	return true;
-#endif
 }
 
-// Close winsocket, if we are using Windows
 void CloseWinSocket( void )
 {
-#ifdef _WIN32
-	WSACleanup( );
-#endif
 }