feat: add multi-bill-edit page for batch bill status updates

- Add getLocationsByMonth server action with aggregation pipeline to calculate hasAttachment
- Add updateMonth server action for bulk bill status updates with path revalidation
- Create multi-bill-edit page at /home/multi-bill-edit/[year]/[month]
- Implement MultiBillEdit component with toggle functionality for all bills
- Add BillToggleBadge component integration for consistent bill display
- Add "set all as paid/unpaid" toggle button for batch operations
- Implement server-side redirect with success message after save
- Add Suspense boundary with loading skeleton
- Update translations for multi-bill-edit feature (Croatian and English)
- Ensure data freshness with unstable_noStore and revalidatePath

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

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

app/ui/MonthLocationList.tsx

@@ -12,6 +12,7 @@ import { useRouter, useSearchParams } from "next/navigation";
 import { ToastContainer, toast } from 'react-toastify';
 import 'react-toastify/dist/ReactToastify.css';
 import { useTranslations } from "next-intl";
+import { MultiBillEditButton } from "../[locale]/home/multi-bill-edit/[year]/[month]/MultiBillEditButton";
 
 const getNextYearMonth = (yearMonth:YearMonth) => {
     const {year, month} = yearMonth;
@@ -84,6 +85,12 @@ export const MonthLocationList:React.FC<MonthLocationListProps  > = ({
             params.delete('locationDeleted');
             messageShown = true;
         }
+
+        if (search.get('bill-multi-edit-saved') === 'true') {
+            toast.success(t("bill-multi-edit-save-success-message"), { theme: "dark" });
+            params.delete('bill-multi-edit-saved');
+            messageShown = true;
+        }
     }, [search, router, t]);
 
     if(!availableYears || !months) {
@@ -128,6 +135,7 @@ export const MonthLocationList:React.FC<MonthLocationListProps  > = ({
                         <div className="flex gap-2 justify-center">
                         <AddLocationButton yearMonth={yearMonth} />
                         <PrintButton yearMonth={yearMonth} />
+                        <MultiBillEditButton yearMonth={yearMonth} />
                         </div>
                     </MonthCard>
                 )