Introduce EXIT_CODE_SUCCESS to standardize successful exit status

Added the definition for EXIT_CODE_SUCCESS in src/error.h and updated the initial value of exit_code in src/stub.c from 0 to EXIT_CODE_SUCCESS. This change standardizes the representation of a successful exit across the application, enhancing code readability and maintainability.

src/error.h

@@ -1,3 +1,5 @@
+// Exit code definitions
+#define EXIT_CODE_SUCCESS ((DWORD)0)
 #define EXIT_CODE_FAILURE ((DWORD)-1)
 
 /**

src/stub.c

@@ -46,7 +46,7 @@ BOOL WINAPI ConsoleHandleRoutine(DWORD dwCtrlType)
 
 int CALLBACK WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
 {
-    DWORD exit_code = 0;
+    DWORD exit_code = EXIT_CODE_SUCCESS;
     MappedFile mapped_file = NULL;
     OperationModes flags = 0;