docs(phase-2): complete context and implementation planning

- Documented comprehensive plan for Phase 2: Rooms and Tasks
- Includes feature scope, requirements, implementation decisions, UI/UX specifics, and scheduling logic
- Updated schema: added Room and Task tables with CRUD and recurrence support
- Added implementation details for room/task templates, cleanliness indicators, and overdue task handling
- Generated Drift schemas for database versioning (v1 → v2) with test coverage

test/drift/household_keeper/generated/schema_v1.dart

@@ -0,0 +1,16 @@
+// dart format width=80
+// GENERATED BY drift_dev, DO NOT MODIFY.
+// ignore_for_file: type=lint,unused_import
+//
+import 'package:drift/drift.dart';
+
+class DatabaseAtV1 extends GeneratedDatabase {
+  DatabaseAtV1(QueryExecutor e) : super(e);
+  @override
+  Iterable<TableInfo<Table, Object?>> get allTables =>
+      allSchemaEntities.whereType<TableInfo<Table, Object?>>();
+  @override
+  List<DatabaseSchemaEntity> get allSchemaEntities => [];
+  @override
+  int get schemaVersion => 1;
+}