Refactored validation logic and centralized employee validators

<SRS> SRS02 : Employee Management </SRS>

<Changes>
 - Moved employee validation logic (active type check, email and phone duplication) to Validator utility
 - Updated service to use util::hasActiveEmployeeOfType, util::isEmailDuplicate, and util::isPhoneDuplicate
 - Integrated validator usage in MenuHelper for input validation
 - Cleaned up formatting and minor inconsistencies
</Changes>

<Review>
Smitha Mohan
</Review>

Trenser.Zenvy/Trenser.Zenvy/utilities/Validator.h

@@ -1,11 +1,21 @@
 #pragma once
 #include<string>
+#include<map>
+#include<memory>
+#include<vector>
 #include<algorithm>
 #include<cctype>
+#include "Enums.h"
+
+class Employee;
 
 namespace util
 {
 	bool isPhoneNumberValid(const std::string&);
 	bool isEmailValid(const std::string&);
 	bool isPasswordValid(const std::string&);
+	bool hasActiveEmployeeOfType(Enums::EmployeeType, const std::map<std::string, std::shared_ptr<Employee>>&);
+	bool isEmailDuplicate(const std::string&, const std::map<std::string, std::shared_ptr<Employee>>&);
+	bool isPhoneDuplicate(const std::string&, const std::map<std::string, std::shared_ptr<Employee>>&);
+	bool isPhoneDuplicate(const std::string&, const std::vector<std::shared_ptr<const Employee>>&);
 }