Fix DataInitializer and make products publicly accessible

src/test/java/com/petshop/backend/util/PasswordHashGenerator.java

@@ -0,0 +1,13 @@
+package com.petshop.backend.util;
+
+import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
+
+public class PasswordHashGenerator {
+    public static void main(String[] args) {
+        BCryptPasswordEncoder encoder = new BCryptPasswordEncoder();
+
+        System.out.println("admin123: " + encoder.encode("admin123"));
+        System.out.println("staff123: " + encoder.encode("staff123"));
+        System.out.println("customer123: " + encoder.encode("customer123"));
+    }
+}