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.dart

@@ -0,0 +1,24 @@
+// dart format width=80
+// GENERATED BY drift_dev, DO NOT MODIFY.
+// ignore_for_file: type=lint,unused_import
+//
+import 'package:drift/drift.dart';
+import 'package:drift/internal/migrations.dart';
+import 'schema_v1.dart' as v1;
+import 'schema_v2.dart' as v2;
+
+class GeneratedHelper implements SchemaInstantiationHelper {
+  @override
+  GeneratedDatabase databaseForVersion(QueryExecutor db, int version) {
+    switch (version) {
+      case 1:
+        return v1.DatabaseAtV1(db);
+      case 2:
+        return v2.DatabaseAtV2(db);
+      default:
+        throw MissingSchemaException(version, versions);
+    }
+  }
+
+  static const versions = const [1, 2];
+}