Rename tenantFirstName to tenantName with updated validation

- Renamed tenantFirstName to tenantName in BillingLocation interface
- Updated LocationEditForm field to accept full name (first and last)
- Set maximum length to 30 characters for tenant name field
- Updated all database operations to use tenantName
- Changed English label from "Tenant First Name" to "Tenant First and Last Name"
- Updated Croatian translations to match (Ime i prezime podstanara)
- Updated form validation schema and error messages
- Removed old tenantLastName-related translations

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

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

app/lib/db-types.ts

@@ -51,8 +51,8 @@ export interface BillingLocation {
     notes: string|null;
     /** (optional) whether to generate 2D code for tenant */
     generateTenantCode?: boolean | null;
-    /** (optional) tenant first name */
-    tenantFirstName?: string | null;
+    /** (optional) tenant name */
+    tenantName?: string | null;
     /** (optional) tenant street */
     tenantStreet?: string | null;
     /** (optional) tenant town */