Add detailed logging and UI refresh for inventory sync

🔍 Debug Improvements:
- Added detailed logging to track sync events
- Print statements show: items received, added, updated, deleted
- Logs Firebase connection status and errors
- Easier to diagnose sync issues

🔄 UI Refresh Fix:
- Added callback system to notify UI when sync occurs
- HomeScreen invalidates providers after Firebase sync
- UI now automatically refreshes when items sync
- No manual refresh needed!

📝 Logging Output:
- 📡 Starting Firebase sync for household: {id}
- 🔄 Received {count} items from Firebase
- ➕ Added new item from Firebase: {name}
- 🔄 Updated item from Firebase: {name}
- 🗑️ Deleting {count} items no longer in Firebase
- ✅ UI refreshed after Firebase sync

✅ Build Status:
- APK: 63.4MB
- All tests passing
- Ready for testing

🎯 How to Test:
1. Install on both phones
2. Check console logs (adb logcat)
3. Add item on Phone A
4. Watch logs on Phone B - should see sync messages
5. If no sync messages → Firebase not configured correctly

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

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

lib/features/household/services/inventory_sync_service.dart

@@ -1,5 +1,6 @@
 import 'dart:async';
 import 'package:cloud_firestore/cloud_firestore.dart';
+import 'package:flutter/foundation.dart';
 import '../../../data/local/hive_database.dart';
 import '../../inventory/models/food_item.dart';
 
@@ -7,18 +8,39 @@ import '../../inventory/models/food_item.dart';
 class InventorySyncService {
   final FirebaseFirestore _firestore = FirebaseFirestore.instance;
   StreamSubscription? _itemsSubscription;
+  final _syncCallbacks = <VoidCallback>[];
+
+  /// Register a callback to be called when sync occurs
+  void addSyncCallback(VoidCallback callback) {
+    _syncCallbacks.add(callback);
+  }
+
+  /// Remove a sync callback
+  void removeSyncCallback(VoidCallback callback) {
+    _syncCallbacks.remove(callback);
+  }
 
   /// Start listening to household items from Firebase
   Future<void> startSync(String householdId) async {
     await stopSync(); // Stop any existing subscription
 
+    print('📡 Starting Firebase sync for household: $householdId');
+
     _itemsSubscription = _firestore
         .collection('households')
         .doc(householdId)
         .collection('items')
         .snapshots()
         .listen((snapshot) async {
+      print('🔄 Received ${snapshot.docs.length} items from Firebase');
       await _handleItemsUpdate(snapshot, householdId);
+
+      // Notify listeners
+      for (final callback in _syncCallbacks) {
+        callback();
+      }
+    }, onError: (error) {
+      print('❌ Firebase sync error: $error');
     });
   }
 
@@ -33,10 +55,13 @@ class InventorySyncService {
     QuerySnapshot snapshot,
     String householdId,
   ) async {
+    print('📦 Processing ${snapshot.docs.length} items from Firebase');
     final box = await HiveDatabase.getFoodBox();
 
     // Track Firebase item IDs
     final firebaseItemIds = <String>{};
+    int newItems = 0;
+    int updatedItems = 0;
 
     for (final doc in snapshot.docs) {
       firebaseItemIds.add(doc.id);
@@ -53,6 +78,8 @@ class InventorySyncService {
         if (existingItem == null) {
           // New item from Firebase - add to local Hive with specific key
           await box.put(itemKey, item);
+          newItems++;
+          print('➕ Added new item from Firebase: ${item.name} (key: $itemKey)');
         } else {
           // Update existing item if Firebase version is newer
           final firebaseModified = DateTime.parse(data['lastModified'] as String);
@@ -61,11 +88,15 @@ class InventorySyncService {
           if (firebaseModified.isAfter(localModified)) {
             // Firebase version is newer - update local
             await box.put(itemKey, item);
+            updatedItems++;
+            print('🔄 Updated item from Firebase: ${item.name} (key: $itemKey)');
           }
         }
       }
     }
 
+    print('📊 Sync stats: $newItems new, $updatedItems updated');
+
     // Delete items that no longer exist in Firebase
     final itemsToDelete = <int>[];
     for (final item in box.values) {
@@ -76,8 +107,11 @@ class InventorySyncService {
       }
     }
 
-    for (final key in itemsToDelete) {
-      await box.delete(key);
+    if (itemsToDelete.isNotEmpty) {
+      print('🗑️ Deleting ${itemsToDelete.length} items that no longer exist in Firebase');
+      for (final key in itemsToDelete) {
+        await box.delete(key);
+      }
     }
   }