Add real-time inventory syncing across devices v1.1.0

🔄 Inventory Sync Features:
- Automatic sync to Firebase when adding/updating/deleting items
- Real-time listener pulls changes from other devices
- Bi-directional sync keeps all household devices in sync
- Conflict resolution based on lastModified timestamp
- Firebase version always wins on conflicts

📱 How It Works:
Device A adds item → syncs to Firebase → Device B receives update
Device B updates item → syncs to Firebase → Device A receives update
Device A deletes item → syncs to Firebase → Device B removes item

🔧 Technical Implementation:
- InventorySyncService: Real-time Firestore listener
- Repository hooks: add/update/delete sync to Firebase
- HomeScreen lifecycle: starts/stops sync automatically
- Conflict resolution: newer timestamp wins
- Local Hive + Cloud Firestore hybrid architecture

📁 New Files:
- lib/features/household/services/inventory_sync_service.dart

✨ Updated Files:
- lib/features/inventory/repositories/inventory_repository_impl.dart
  - Added Firebase sync on add/update/delete operations
  - Maintains local Hive for offline access
- lib/features/home/screens/home_screen.dart
  - Starts sync service on init if in household
  - Stops sync service on dispose

⚠️ Requirements:
- Firebase must be configured (see FIREBASE_SETUP.md)
- Internet connection required for cross-device sync
- Local Hive works offline, syncs when online

✅ Build Status:
- APK: 63.4MB
- Package: com.github.mystiatech.sage
- Version: 1.1.0+2

🎯 Next Steps for User:
1. Set up Firebase (FIREBASE_SETUP.md)
2. Replace google-services.json with real file
3. Rebuild APK
4. Install on both devices
5. Create/join household
6. Add items → they sync! 🎉

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

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

lib/features/inventory/repositories/inventory_repository_impl.dart

@@ -1,11 +1,13 @@
 import 'package:hive/hive.dart';
 import '../../../data/local/hive_database.dart';
 import '../../settings/models/app_settings.dart';
+import '../../household/services/firebase_household_service.dart';
 import '../models/food_item.dart';
 import 'inventory_repository.dart';
 
-/// Hive implementation of InventoryRepository
+/// Hive implementation of InventoryRepository with Firebase sync
 class InventoryRepositoryImpl implements InventoryRepository {
+  final _firebaseService = FirebaseHouseholdService();
   Future<Box<FoodItem>> get _box async => await HiveDatabase.getFoodBox();
 
   /// Get the current household ID from settings
@@ -47,17 +49,57 @@ class InventoryRepositoryImpl implements InventoryRepository {
     final box = await _box;
     item.lastModified = DateTime.now();
     await box.add(item);
+
+    // Sync to Firebase if in a household
+    if (item.householdId != null && item.key != null) {
+      try {
+        await _firebaseService.addFoodItem(
+          item.householdId!,
+          item,
+          item.key.toString(),
+        );
+      } catch (e) {
+        print('Failed to sync item to Firebase: $e');
+      }
+    }
   }
 
   @override
   Future<void> updateItem(FoodItem item) async {
     item.lastModified = DateTime.now();
     await item.save();
+
+    // Sync to Firebase if in a household
+    if (item.householdId != null && item.key != null) {
+      try {
+        await _firebaseService.updateFoodItem(
+          item.householdId!,
+          item,
+          item.key.toString(),
+        );
+      } catch (e) {
+        print('Failed to sync item update to Firebase: $e');
+      }
+    }
   }
 
   @override
   Future<void> deleteItem(int id) async {
     final box = await _box;
+    final item = box.get(id);
+
+    // Sync deletion to Firebase if in a household
+    if (item != null && item.householdId != null) {
+      try {
+        await _firebaseService.deleteFoodItem(
+          item.householdId!,
+          id.toString(),
+        );
+      } catch (e) {
+        print('Failed to sync item deletion to Firebase: $e');
+      }
+    }
+
     await box.delete(id);
   }