refactor: improve notification naming and introduce type-safe enums

- Rename billFwd* to billsNotification* for clarity
- Rename rentDueNotification* to rentNotification* for consistency
- Rename utilBillsProofOfPayment to billsProofOfPayment
- Introduce enums for type safety:
  - BillsNotificationStrategy (WhenPayed, WhenAttached)
  - BillsNotificationStatus (Scheduled, Sent, Failed)
  - RentNotificationStatus (Sent, Failed)
- Replace "pending" status with "scheduled" for better semantics
- Fix function names to proper camelCase
- Fix incorrect import path in web-app/app/lib/format.ts

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

email-worker/src/lib/emailSenders.ts

@@ -1,5 +1,5 @@
 import { Db, ObjectId } from 'mongodb';
-import { BillingLocation, EmailStatus, UserSettings, generateShareId } from '@evidencija-rezija/shared-code';
+import { BillingLocation, BillsNotificationStatus, EmailStatus, RentNotificationStatus, UserSettings, generateShareId } from '@evidencija-rezija/shared-code';
 import { sendEmail } from './mailgunService';
 import { createLogger } from './logger';
 import { loadAndRender } from './emailTemplates';
@@ -115,11 +115,11 @@ export async function sendRentDueNotifications(db: Db, budget: number): Promise<
             'yearMonth.year': currentYear,
             'yearMonth.month': currentMonth,
             'tenantEmailStatus': EmailStatus.Verified,
-            'rentDueNotificationEnabled': true,
+            'rentNotificationEnabled': true,
             'rentDueDay': currentDay,
             $or: [
-                { 'rentDueNotificationStatus': { $exists: false } },
-                { 'rentDueNotificationStatus': null }
+                { 'rentNotificationStatus': { $exists: false } },
+                { 'rentNotificationStatus': null }
             ]
         })
         .toArray();
@@ -170,10 +170,10 @@ export async function sendRentDueNotifications(db: Db, budget: number): Promise<
         });
 
         // Update location status
-        const newStatus = success ? 'sent' : 'failed';
+        const newStatus = success ? RentNotificationStatus.Sent : RentNotificationStatus.Failed;
         await db.collection<BillingLocation>('lokacije').updateOne(
             { _id: location._id },
-            { $set: { rentDueNotificationStatus: newStatus } }
+            { $set: { rentNotificationStatus: newStatus } }
         );
 
         if (success) {
@@ -213,8 +213,8 @@ export async function sendUtilityBillsNotifications(db: Db, budget: number): Pro
             'yearMonth.year': currentYear,
             'yearMonth.month': currentMonth,
             'tenantEmailStatus': EmailStatus.Verified,
-            'billFwdEnabled': true,
-            'billFwdStatus': 'pending'
+            'billsNotificationEnabled': true,
+            'billsNotificationStatus': BillsNotificationStatus.Scheduled
         })
         .toArray();
 
@@ -263,10 +263,10 @@ export async function sendUtilityBillsNotifications(db: Db, budget: number): Pro
         });
 
         // Update location status
-        const newStatus = success ? 'sent' : 'failed';
+        const newStatus = success ? BillsNotificationStatus.Sent : BillsNotificationStatus.Failed;
         await db.collection<BillingLocation>('lokacije').updateOne(
             { _id: location._id },
-            { $set: { billFwdStatus: newStatus } }
+            { $set: { billsNotificationStatus: newStatus } }
         );
 
         if (success) {