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/lib/db-types.ts

@@ -53,8 +53,6 @@ export interface BillingLocation {
     generateTenantCode?: boolean | null;
     /** (optional) tenant first name */
     tenantFirstName?: string | null;
-    /** (optional) tenant last name */
-    tenantLastName?: string | null;
     /** (optional) tenant street */
     tenantStreet?: string | null;
     /** (optional) tenant town */