Add household sharing feature

✨ Features:
- Create household with 6-character shareable code
- Join existing household with code
- View household members and owner
- Leave household functionality
- Automatic inventory filtering by household
- Persistent household settings across app updates

🔧 Technical changes:
- Added Household model with Hive adapter (typeId: 4)
- Updated AppSettings with userName and currentHouseholdId fields
- Modified InventoryRepository to filter items by household
- Updated Add Item screen to set householdId on new items
- Added HouseholdScreen with full CRUD operations
- Integrated household sharing into Settings navigation

🎯 Behavior:
- Users not in a household see only their personal items
- Users in a household see shared household items
- New items automatically tagged with current household

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

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

lib/features/settings/screens/settings_screen.dart

@@ -6,6 +6,7 @@ import '../models/app_settings.dart';
 import '../../notifications/services/discord_service.dart';
 import 'privacy_policy_screen.dart';
 import 'terms_of_service_screen.dart';
+import 'household_screen.dart';
 
 class SettingsScreen extends StatefulWidget {
   const SettingsScreen({super.key});
@@ -91,6 +92,29 @@ class _SettingsScreenState extends State<SettingsScreen> {
 
           const Divider(),
 
+          // Sharing Section
+          _buildSectionHeader('Sharing'),
+          ListTile(
+            title: const Text('Household Sharing'),
+            subtitle: Text(_settings!.currentHouseholdId != null
+                ? 'Connected to household'
+                : 'Share inventory with family'),
+            leading: const Icon(Icons.group, color: AppColors.primary),
+            trailing: const Icon(Icons.chevron_right),
+            onTap: () async {
+              await Navigator.push(
+                context,
+                MaterialPageRoute(
+                  builder: (context) => const HouseholdScreen(),
+                ),
+              );
+              // Reload settings after returning from household screen
+              _loadSettings();
+            },
+          ),
+
+          const Divider(),
+
           // Display Section
           _buildSectionHeader('Display'),
           ListTile(