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/lib/actions/monthActions.ts

@@ -5,7 +5,9 @@ import { ObjectId } from 'mongodb';
 import { Bill, BillingLocation, YearMonth } from '../db-types';
 import { AuthenticatedUser } from '../types/next-auth';
 import { withUser } from '../auth';
-import { unstable_noStore as noStore } from 'next/cache';
+import { unstable_noStore as noStore, unstable_noStore, revalidatePath } from 'next/cache';
+import { getLocale } from 'next-intl/server';
+import { gotoHomeWithMessage } from './navigationActions';
 
 /**
  * Server-side action which adds a new month to the database
@@ -82,3 +84,137 @@ export const fetchAvailableYears = withUser(async (user:AuthenticatedUser) => {
 
     return(sortedYears);
 })
+
+/**
+ * Fetches all locations for a specific month for the authenticated user
+ * Only projects essential fields needed for the multi-bill-edit page
+ * @param yearMonth - The year and month to fetch
+ * @returns Array of locations with minimal bill data
+ */
+export const getLocationsByMonth = withUser(async (user: AuthenticatedUser, yearMonth: YearMonth) => {
+    
+    unstable_noStore();
+
+    const { id: userId } = user;
+    const dbClient = await getDbClient();
+
+    // Use aggregation pipeline to calculate hasAttachment field
+    const locations = await dbClient.collection<BillingLocation>("lokacije")
+        .aggregate([
+            {
+                $match: {
+                    userId,
+                    yearMonth: {
+                        year: yearMonth.year,
+                        month: yearMonth.month,
+                    }
+                }
+            },
+            {
+                $addFields: {
+                    _id: { $toString: "$_id" },
+                    bills: {
+                        $map: {
+                            input: "$bills",
+                            as: "bill",
+                            in: {
+                                _id: { $toString: "$$bill._id" },
+                                name: "$$bill.name",
+                                paid: "$$bill.paid",
+                                hasAttachment: { $ne: ["$$bill.attachment", null] },
+                                proofOfPayment: "$$bill.proofOfPayment",
+                            },
+                        },
+                    }
+                }
+            },
+            {
+                $project: {
+                    "_id": 1,
+                    "name": 1,
+                    "yearMonth.year": 1,
+                    "yearMonth.month": 1,
+                    "bills._id": 1,
+                    "bills.name": 1,
+                    "bills.paid": 1,
+                    "bills.hasAttachment": 1,
+                    "bills.proofOfPayment.uploadedAt": 1,
+                }
+            },
+            {
+                $sort: {
+                    name: 1,
+                },
+            },
+        ])
+        .toArray();
+
+    return locations as Array<BillingLocation>;
+});
+
+/**
+ * Updates the paid status of bills for locations in a specific month
+ * @param yearMonth - The year and month to update
+ * @param updates - Array of updates with locationId, billId, and paid status
+ * @returns Success status
+ */
+export const updateMonth = withUser(async (
+    user: AuthenticatedUser,
+    yearMonth: YearMonth,
+    updates: Array<{ locationId: string; billId: string; paid: boolean }>
+) => {
+    unstable_noStore();
+
+    const { id: userId } = user;
+    const dbClient = await getDbClient();
+
+    // Group updates by location to minimize database operations
+    const updatesByLocation = updates.reduce((acc, update) => {
+        if (!acc[update.locationId]) {
+            acc[update.locationId] = [];
+        }
+        acc[update.locationId].push(update);
+        return acc;
+    }, {} as Record<string, typeof updates>);
+
+    // Perform bulk updates
+    const updatePromises = Object.entries(updatesByLocation).map(
+        async ([locationId, locationUpdates]) => {
+            // For each bill update in this location
+            const billUpdatePromises = locationUpdates.map(({ billId, paid }) =>
+                dbClient.collection<BillingLocation>("lokacije").updateOne(
+                    {
+                        _id: locationId,
+                        userId, // Ensure the location belongs to the authenticated user
+                        yearMonth: {
+                            year: yearMonth.year,
+                            month: yearMonth.month,
+                        },
+                        'bills._id': billId,
+                    },
+                    {
+                        $set: {
+                            'bills.$.paid': paid,
+                        },
+                    }
+                )
+            );
+
+            return Promise.all(billUpdatePromises);
+        }
+    );
+
+    await Promise.all(updatePromises);
+
+    // Revalidate the home page and multi-edit page to show fresh data
+    revalidatePath('/home');
+    revalidatePath(`/home/multi-bill-edit/${yearMonth.year}/${yearMonth.month}`);
+
+    // Redirect to home page with year and month parameters, including success message
+    if (yearMonth) {
+        const locale = await getLocale();
+        await gotoHomeWithMessage(locale, 'bill-multi-edit-saved', yearMonth);
+    }
+
+    return { success: true };
+});