Implement Model Refactoring

<UserStory> 1957: Model Refactoring </UserStory>

UserStory #1957

<Changes>

1. Added SerializedRecords.h dependency and forward declaration for SerializedInventoryItem
   to support fixed-size record storage.

2. Replaced CSV-based serialization in InventoryItem with serialize() method returning
   SerializedInventoryItem structure.

3. Replaced CSV-based deserialization logic with deserialize() method that reconstructs
   InventoryItem directly from SerializedInventoryItem record.

4. Removed legacy CSV parsing, header generation, and exception handling tied to string-based
   serialization.

5. Updated InventoryItem class interface in InventoryItem.h to use SerializedInventoryItem
   types instead of std::string serialization APIs.

</Changes>

<Test>

N/A

</Test>

<Review>

Sreeja Reghukumar

</Review>

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/models/InventoryItem.h

@@ -6,11 +6,12 @@ Author: Trenser
 Date: 19-May-2026
 */
 
-
 #pragma once
 #include <string>
 #include "Enums.h"
 
+struct SerializedInventoryItem;
+
 class InventoryItem
 {
 private:
@@ -34,7 +35,6 @@ public:
     void setQuantity(int quantity);
     void setPrice(double price);
     void setState(util::State status);
-    std::string serialize() const;
-    static InventoryItem* deserialize(const std::string&);
-    static std::string getHeaders();
+    SerializedInventoryItem serialize() const;
+    static InventoryItem* deserialize(const SerializedInventoryItem&);
 };