fix(client): age validate logic

Author: Pumpkin-Nguyen

bigbid-client/src/main/java/com/bigbid/client/controller/LoginController.java

@@ -170,7 +170,7 @@ private void handleRegister() {
             return;
         }
 
-        if (LocalDate.now().minusYears(16).isAfter(dob)) {
+        if (dob.minusYears(16).isAfter(LocalDate.now())) {
             AlertHelper.showWarning(
                     "Age Requirement", "You must be at least 16 years old to register.");
             return;