Remove tenantLastName field from LocationEditForm and database

- Removed tenantLastName from BillingLocation interface
- Updated LocationEditForm to remove tenantLastName input field
- Removed tenantLastName from all database operations (insert and update)
- Updated form validation schema to remove tenantLastName validation
- Updated ViewLocationCard to use only tenantFirstName for payer name
- Removed tenantLastName from tenant field state tracking

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/ui/ViewLocationCard.tsx

@@ -16,7 +16,7 @@ export interface ViewLocationCardProps {
 
 export const ViewLocationCard:FC<ViewLocationCardProps> = ({location, userSettings}) => {
 
-    const { _id, name, yearMonth, bills, tenantFirstName, tenantLastName, tenantStreet, tenantTown } = location;
+    const { _id, name, yearMonth, bills, tenantFirstName, tenantStreet, tenantTown } = location;
 
     const t = useTranslations("home-page.location-card");
 
@@ -25,7 +25,7 @@ export const ViewLocationCard:FC<ViewLocationCardProps> = ({location, userSettin
 
     const paymentParams:PaymentParams = {
         Iznos: (monthlyExpense/100).toFixed(2).replace(".",","),
-        ImePlatitelja: (tenantFirstName && tenantLastName) ? `${tenantFirstName} ${tenantLastName}` : "",
+        ImePlatitelja: tenantFirstName ?? "",
         AdresaPlatitelja: tenantStreet ?? "",
         SjedistePlatitelja: tenantTown ?? "",
         Primatelj: (userSettings?.firstName && userSettings?.lastName) ? `${userSettings.firstName} ${userSettings.lastName}` : "",