feat: Add desktop screenshots

frontend/src/pages/GuidePage/sections/VehiclesSection.tsx

@@ -34,7 +34,7 @@ export const VehiclesSection = () => {
         </ul>
 
         <GuideScreenshot
-          src="/guide/vehicles-list-desktop.webp"
+          src="/guide/vehicles-list-desktop.png"
           alt="Vehicles page showing grid of vehicle cards with details"
           caption="The Vehicles page displays all your vehicles in a searchable grid"
         />
@@ -87,7 +87,7 @@ export const VehiclesSection = () => {
         />
 
         <GuideScreenshot
-          src="/guide/add-vehicle-form-desktop.webp"
+          src="/guide/add-vehicle-form-desktop.png"
           alt="Add Vehicle form showing cascading dropdowns for specifications"
           caption="The Add Vehicle form with cascading dropdowns for easy data entry"
         />
@@ -139,7 +139,7 @@ export const VehiclesSection = () => {
         </ol>
 
         <GuideScreenshot
-          src="/guide/vin-decode-desktop.webp"
+          src="/guide/vin-decode-desktop.png"
           alt="VIN Decode feature showing auto-populated vehicle specifications"
           caption="The VIN Decode feature automatically fills in vehicle details from the NHTSA database"
         />
@@ -173,7 +173,7 @@ export const VehiclesSection = () => {
         </ul>
 
         <GuideScreenshot
-          src="/guide/vehicle-detail-desktop.webp"
+          src="/guide/vehicle-detail-desktop.png"
           alt="Vehicle Detail page showing complete vehicle information and records"
           caption="The Vehicle Detail page displays all information and records for a single vehicle"
         />