Replace billedToTenant boolean with billedTo enum

Migrated from boolean checkbox to enum-based radio buttons for better
flexibility and clarity in tracking bill payment responsibility.

Changes:
- Added BilledTo enum with values 'tenant' and 'landlord'
- Replaced Bill.billedToTenant (boolean) with Bill.billedTo (enum)
- Updated BillEditForm to use radio buttons instead of checkbox
- Updated billActions to handle billedTo enum values
- Updated all display filtering to use enum comparison
- Updated printActions barcode filtering
- Updated translations for radio button labels (en/hr)

The billedTo property is optional for backward compatibility -
undefined values default to BilledTo.Tenant, maintaining current
behavior where only tenant bills are displayed and calculated.

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

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

app/lib/db-types.ts

@@ -31,6 +31,11 @@ export interface BillingLocation {
     notes: string|null;
 };
 
+export enum BilledTo {
+    Tenant = "tenant",
+    Landlord = "landlord"
+}
+
 /** Bill basic data */
 export interface Bill {
     _id: string;
@@ -38,8 +43,8 @@ export interface Bill {
     name: string;
     /** is the bill paid */
     paid: boolean;
-    /** true if tenant to cover the bill */
-    billedToTenant: boolean;
+    /** who is billed for the bill */
+    billedTo?: BilledTo;
     /** payed amount amount in cents */
     payedAmount?: number | null;
     /** attached document (optional) */