fix: improve error handling by using localized message in GlobalExceptionHandler

Author: noobdevsam

src/main/java/com/example/springprojectsteganographytool/exceptions/GlobalExceptionHandler.java

@@ -153,7 +153,7 @@ public ProblemDetail handleGeneric(
         // logger.error("Unhandled exception", ex);
         var pd = ProblemDetail.forStatusAndDetail(
                 HttpStatus.INTERNAL_SERVER_ERROR,
-                "An unexpected error occurred."
+                ex.getLocalizedMessage()
         );
         var traceId = MDC.get("traceId");