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/models/household.g.dart

@@ -0,0 +1,53 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'household.dart';
+
+// **************************************************************************
+// TypeAdapterGenerator
+// **************************************************************************
+
+class HouseholdAdapter extends TypeAdapter<Household> {
+  @override
+  final int typeId = 4;
+
+  @override
+  Household read(BinaryReader reader) {
+    final numOfFields = reader.readByte();
+    final fields = <int, dynamic>{
+      for (int i = 0; i < numOfFields; i++) reader.readByte(): reader.read(),
+    };
+    return Household(
+      id: fields[0] as String,
+      name: fields[1] as String,
+      ownerName: fields[2] as String,
+      createdAt: fields[3] as DateTime?,
+      members: (fields[4] as List?)?.cast<String>(),
+    );
+  }
+
+  @override
+  void write(BinaryWriter writer, Household obj) {
+    writer
+      ..writeByte(5)
+      ..writeByte(0)
+      ..write(obj.id)
+      ..writeByte(1)
+      ..write(obj.name)
+      ..writeByte(2)
+      ..write(obj.ownerName)
+      ..writeByte(3)
+      ..write(obj.createdAt)
+      ..writeByte(4)
+      ..write(obj.members);
+  }
+
+  @override
+  int get hashCode => typeId.hashCode;
+
+  @override
+  bool operator ==(Object other) =>
+      identical(this, other) ||
+      other is HouseholdAdapter &&
+          runtimeType == other.runtimeType &&
+          typeId == other.typeId;
+}