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>

web-app/app/ui/LocationCard.tsx

@@ -24,7 +24,7 @@ export const LocationCard: FC<LocationCardProps> = ({ location, currency }) => {
         bills,
         seenByTenantAt,
         // NOTE: only the fileName is projected from the DB to reduce data transfer
-        utilBillsProofOfPayment,
+        billsProofOfPayment,
         tenantEmail,
         tenantEmailStatus,
     } = location;
@@ -70,7 +70,7 @@ export const LocationCard: FC<LocationCardProps> = ({ location, currency }) => {
                     </Link>
                     <ShareIcon className="h-[1em] w-[1em] cursor-pointer text-2xl inline hover:text-red-500" title="create sharable link" onClick={handleCopyLinkClick} />
                 </div>
-                { totalUnpaid > 0 || totalPayed > 0 || seenByTenantAt || utilBillsProofOfPayment?.uploadedAt || (tenantEmail && tenantEmailStatus && tenantEmailStatus !== EmailStatus.Verified) ?
+                { totalUnpaid > 0 || totalPayed > 0 || seenByTenantAt || billsProofOfPayment?.uploadedAt || (tenantEmail && tenantEmailStatus && tenantEmailStatus !== EmailStatus.Verified) ?
                     <>
                         <div className="flex ml-1">
                             <div className="divider divider-horizontal p-0 m-0"></div>
@@ -125,7 +125,7 @@ export const LocationCard: FC<LocationCardProps> = ({ location, currency }) => {
                                         </span>
                                     </div>
                                 )}
-                                {utilBillsProofOfPayment?.uploadedAt && (
+                                {billsProofOfPayment?.uploadedAt && (
                                     <Link
                                         href={`/share/proof-of-payment/${_id}/`}
                                         target="_blank"