[03-Developer] #226 Catalog Gallery 구현

- Drift schema v2: Protocols.category CHECK 6→7 (light_circadian/sleep/movement/
  nutrition/focus_cognition/recovery_stress/emotion_relationship). schemaVersion
  1→2 + onUpgrade migrateV1ToV2 (DROP+CREATE+reseed flag 클리어).
- protocols.json 34 항목 v2 재분류 (1차 효과 기준). emotion_relationship 0 매핑.
- 도메인: DisplayCategory enum (8) + CatalogItem sealed (Protocol/Break/Diet).
- 데이터: CatalogRepository.all/byId/referencesByIds (3 source 통합).
- 상태: catalog_providers.dart (catalogItems / groupedByCategory / refsByIds).
- UI: ProtocolGalleryScreen (카테고리 칩 + 카드 그리드) + ProtocolPreviewScreen
  (모든 필드 + reference 펼치기 + "내 습관으로" disabled placeholder) +
  CatalogCard / CategoryChipRow / ReferenceExpandCard. HabitListScreen 빈
  상태 CTA + AppBar 액션.
- 테스트: migration_v1_to_v2 3건 + display_category 5건 + catalog_repository
  9건 + gallery widget 3건 + preview widget 3건 = 23 신규. 기존 88 회귀 0,
  flutter analyze 0 issues. 110 passed / 1 skipped.

설계서: docs/design/226-catalog-gallery/{README, fn-catalog_repository,
fn-migration_v1_to_v2}.md + ADR-0004.

Refs #226

app/test/ui/protocol_gallery_screen_test.dart

@@ -0,0 +1,83 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:life_helper/domain/catalog/catalog_item.dart';
+import 'package:life_helper/domain/catalog/display_category.dart';
+import 'package:life_helper/state/catalog_providers.dart';
+import 'package:life_helper/ui/screens/protocol_gallery_screen.dart';
+
+ProtocolCatalogItem _protocol(
+        {required String id,
+        required String title,
+        required DisplayCategory dc}) =>
+    ProtocolCatalogItem(
+      id: id,
+      title: title,
+      titleEn: null,
+      summary: '$title 요약',
+      displayCategory: dc,
+      evidenceStrength: 'strong_rct',
+      referenceIds: const [],
+      what: 'w',
+      whenText: 'wn',
+      dose: 'd',
+      why: 'y',
+      how: const [],
+      checkText: 'c',
+      caution: null,
+      defaultAnchor: null,
+      minDoseForStart: null,
+      sourceDoc: null,
+    );
+
+void main() {
+  final fakeItems = [
+    _protocol(id: 'a1', title: '아침 햇빛', dc: DisplayCategory.lightCircadian),
+    _protocol(id: 's1', title: '수면 스택', dc: DisplayCategory.sleep),
+    _protocol(id: 's2', title: '카페인', dc: DisplayCategory.sleep),
+  ];
+
+  Widget buildHarness(List<CatalogItem> items) {
+    return ProviderScope(
+      overrides: [
+        catalogItemsProvider.overrideWith((ref) async => items),
+      ],
+      child: const MaterialApp(home: ProtocolGalleryScreen()),
+    );
+  }
+
+  testWidgets('카테고리 칩 + 카드 표시', (tester) async {
+    await tester.pumpWidget(buildHarness(fakeItems));
+    await tester.pump(); // resolve future
+
+    // 칩: 전체 + lightCircadian + sleep (2 카테고리만 — 빈 카테고리 미표시)
+    expect(find.text('전체'), findsOneWidget);
+    expect(find.text('빛/일주기'), findsOneWidget);
+    expect(find.text('수면'), findsOneWidget);
+    expect(find.text('영양'), findsNothing); // 빈 카테고리는 안 보임
+
+    // 카드 3개
+    expect(find.text('아침 햇빛'), findsOneWidget);
+    expect(find.text('수면 스택'), findsOneWidget);
+    expect(find.text('카페인'), findsOneWidget);
+  });
+
+  testWidgets('칩 선택 시 필터링', (tester) async {
+    await tester.pumpWidget(buildHarness(fakeItems));
+    await tester.pump();
+
+    // 수면 칩 선택
+    await tester.tap(find.text('수면'));
+    await tester.pump();
+
+    expect(find.text('아침 햇빛'), findsNothing);
+    expect(find.text('수면 스택'), findsOneWidget);
+    expect(find.text('카페인'), findsOneWidget);
+  });
+
+  testWidgets('빈 결과 → "항목이 없습니다"', (tester) async {
+    await tester.pumpWidget(buildHarness(const []));
+    await tester.pump();
+    expect(find.text('항목이 없습니다.'), findsOneWidget);
+  });
+}