[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/lib/ui/screens/habit_list_screen.dart

@@ -4,6 +4,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import '../../state/providers.dart';
 import 'check_in_screen.dart';
 import 'habit_create_screen.dart';
+import 'protocol_gallery_screen.dart';
 import 'settings_screen.dart';
 import 'streak_screen.dart';
 
@@ -19,6 +20,11 @@ class HabitListScreen extends ConsumerWidget {
       appBar: AppBar(
         title: const Text('습관'),
         actions: [
+          IconButton(
+            icon: const Icon(Icons.search),
+            tooltip: '카탈로그 탐색',
+            onPressed: () => _openGallery(context),
+          ),
           IconButton(
             icon: const Icon(Icons.settings),
             tooltip: '설정',
@@ -38,8 +44,25 @@ class HabitListScreen extends ConsumerWidget {
           error: (e, st) => Center(child: Text('로드 실패: $e')),
           data: (habits) {
             if (habits.isEmpty) {
-              return const Center(
-                child: Text('아직 습관이 없습니다. + 버튼으로 추가하세요.'),
+              return Center(
+                child: Column(
+                  mainAxisSize: MainAxisSize.min,
+                  children: [
+                    const Padding(
+                      padding: EdgeInsets.symmetric(horizontal: 24),
+                      child: Text(
+                        '아직 습관이 없습니다.\n+ 버튼으로 추가하거나, 카탈로그에서 골라보세요.',
+                        textAlign: TextAlign.center,
+                      ),
+                    ),
+                    const SizedBox(height: 16),
+                    FilledButton.icon(
+                      onPressed: () => _openGallery(context),
+                      icon: const Icon(Icons.search),
+                      label: const Text('🔍 카탈로그 탐색'),
+                    ),
+                  ],
+                ),
               );
             }
             return ListView.separated(
@@ -83,4 +106,10 @@ class HabitListScreen extends ConsumerWidget {
       ),
     );
   }
+
+  void _openGallery(BuildContext context) {
+    Navigator.of(context).push(MaterialPageRoute(
+      builder: (_) => const ProtocolGalleryScreen(),
+    ));
+  }
 }

app/lib/ui/screens/protocol_gallery_screen.dart

@@ -0,0 +1,79 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import '../../domain/catalog/catalog_item.dart';
+import '../../domain/catalog/display_category.dart';
+import '../../state/catalog_providers.dart';
+import '../widgets/catalog_card.dart';
+import '../widgets/category_chip_row.dart';
+import 'protocol_preview_screen.dart';
+
+class ProtocolGalleryScreen extends ConsumerStatefulWidget {
+  const ProtocolGalleryScreen({super.key});
+
+  @override
+  ConsumerState<ProtocolGalleryScreen> createState() =>
+      _ProtocolGalleryScreenState();
+}
+
+class _ProtocolGalleryScreenState extends ConsumerState<ProtocolGalleryScreen> {
+  DisplayCategory? _selected;
+
+  @override
+  Widget build(BuildContext context) {
+    final groupedAsync = ref.watch(groupedByCategoryProvider);
+    return Scaffold(
+      appBar: AppBar(title: const Text('카탈로그 탐색')),
+      body: groupedAsync.when(
+        loading: () => const Center(child: CircularProgressIndicator()),
+        error: (e, _) => Center(child: Text('로드 실패: $e')),
+        data: (grouped) {
+          final categories = DisplayCategory.values
+              .where((c) => grouped.containsKey(c))
+              .toList();
+          final items = _selected == null
+              ? grouped.values.expand((e) => e).toList()
+              : (grouped[_selected] ?? const <CatalogItem>[]);
+          // Sort within filtered view by id (consistent with repo sort).
+          items.sort((a, b) {
+            final c = a.displayCategory.index - b.displayCategory.index;
+            return c != 0 ? c : a.id.compareTo(b.id);
+          });
+          return Column(
+            children: [
+              CategoryChipRow(
+                categories: categories,
+                selected: _selected,
+                onSelect: (c) => setState(() => _selected = c),
+              ),
+              Expanded(
+                child: items.isEmpty
+                    ? const Center(child: Text('항목이 없습니다.'))
+                    : GridView.builder(
+                        padding: const EdgeInsets.all(12),
+                        gridDelegate:
+                            const SliverGridDelegateWithMaxCrossAxisExtent(
+                          maxCrossAxisExtent: 240,
+                          mainAxisExtent: 160,
+                          crossAxisSpacing: 8,
+                          mainAxisSpacing: 8,
+                        ),
+                        itemCount: items.length,
+                        itemBuilder: (context, i) => CatalogCard(
+                          item: items[i],
+                          onTap: () => Navigator.of(context).push(
+                            MaterialPageRoute(
+                              builder: (_) =>
+                                  ProtocolPreviewScreen(item: items[i]),
+                            ),
+                          ),
+                        ),
+                      ),
+              ),
+            ],
+          );
+        },
+      ),
+    );
+  }
+}

app/lib/ui/screens/protocol_preview_screen.dart

@@ -0,0 +1,207 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import '../../domain/catalog/catalog_item.dart';
+import '../../state/catalog_providers.dart';
+import '../widgets/reference_expand_card.dart';
+
+class ProtocolPreviewScreen extends ConsumerWidget {
+  const ProtocolPreviewScreen({super.key, required this.item});
+
+  final CatalogItem item;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text(item.title, maxLines: 1, overflow: TextOverflow.ellipsis),
+      ),
+      body: ListView(
+        padding: const EdgeInsets.fromLTRB(16, 16, 16, 96),
+        children: [
+          _Header(item: item),
+          const SizedBox(height: 16),
+          ..._buildBody(context),
+          const SizedBox(height: 24),
+          _References(referenceIds: item.referenceIds),
+        ],
+      ),
+      bottomNavigationBar: const _ImportFooter(),
+    );
+  }
+
+  List<Widget> _buildBody(BuildContext context) {
+    return switch (item) {
+      ProtocolCatalogItem p => [
+          _section(context, '무엇 (What)', p.what),
+          _section(context, '언제 (When)', p.whenText),
+          _section(context, '도즈 (Dose)', p.dose),
+          _section(context, '왜 (Why)', p.why),
+          if (p.how.isNotEmpty) _howSection(context, p.how),
+          _section(context, '체크 (Check)', p.checkText),
+          if (p.caution != null) _section(context, '주의 (Caution)', p.caution!),
+          if (p.defaultAnchor != null)
+            _section(context, '기본 앵커', _anchorText(p.defaultAnchor!)),
+          if (p.minDoseForStart != null)
+            _section(context, '최소 도즈 (시작용)', p.minDoseForStart!),
+          if (p.sourceDoc != null)
+            _section(context, '출처 문서', p.sourceDoc!),
+        ],
+      BreakCatalogItem b => [
+          _section(context, '요약 (Huberman)', b.hubermanSummary),
+          _section(context, '구분', b.breakCategory),
+          if (b.phases.isNotEmpty)
+            _section(context, '단계', b.phases.join(' / ')),
+          if (b.defaultCommonFrames.isNotEmpty)
+            _section(context, '기본 공통 프레임',
+                b.defaultCommonFrames.join(', ')),
+          if (b.tools.isNotEmpty)
+            _section(context, '도구', b.tools.join(', ')),
+          if (b.medicalWarning != null)
+            _section(context, '의료 경고', b.medicalWarning!),
+        ],
+      DietCatalogItem d => [
+          _section(context, '핵심', d.core),
+          if (d.strengths.isNotEmpty)
+            _section(context, '강점', d.strengths.join('\n• ')),
+          if (d.weaknesses.isNotEmpty)
+            _section(context, '약점', d.weaknesses.join('\n• ')),
+          if (d.koreanContextFit != null)
+            _section(context, '한국 컨텍스트 적합도', d.koreanContextFit!),
+          if (d.starterLevers.isNotEmpty)
+            _section(context, '시작 레버', d.starterLevers.join(', ')),
+          if (d.medicalWarning != null)
+            _section(context, '의료 경고', d.medicalWarning!),
+          if (d.linkedProtocolIds.isNotEmpty)
+            _section(context, '연결 프로토콜', d.linkedProtocolIds.join(', ')),
+        ],
+    };
+  }
+
+  String _anchorText(Map<String, dynamic> m) {
+    final when = m['when'] ?? '';
+    final after = m['after_what'] ?? '';
+    if (when == '' && after == '') return m.toString();
+    return [if (when != '') 'when: $when', if (after != '') 'after: $after']
+        .join(' · ');
+  }
+
+  Widget _section(BuildContext context, String label, String body) {
+    return Padding(
+      padding: const EdgeInsets.only(bottom: 12),
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          Text(label, style: Theme.of(context).textTheme.labelLarge),
+          const SizedBox(height: 4),
+          Text(body, style: Theme.of(context).textTheme.bodyMedium),
+        ],
+      ),
+    );
+  }
+
+  Widget _howSection(BuildContext context, List<String> steps) {
+    return Padding(
+      padding: const EdgeInsets.only(bottom: 12),
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          Text('어떻게 (How)', style: Theme.of(context).textTheme.labelLarge),
+          const SizedBox(height: 4),
+          for (var i = 0; i < steps.length; i++)
+            Padding(
+              padding: const EdgeInsets.only(bottom: 2),
+              child: Text('${i + 1}. ${steps[i]}',
+                  style: Theme.of(context).textTheme.bodyMedium),
+            ),
+        ],
+      ),
+    );
+  }
+}
+
+class _Header extends StatelessWidget {
+  const _Header({required this.item});
+  final CatalogItem item;
+
+  @override
+  Widget build(BuildContext context) {
+    final dc = item.displayCategory;
+    return Row(
+      children: [
+        Icon(dc.icon, size: 20),
+        const SizedBox(width: 8),
+        Expanded(
+          child: Column(
+            crossAxisAlignment: CrossAxisAlignment.start,
+            children: [
+              Text(dc.label,
+                  style: Theme.of(context).textTheme.labelMedium?.copyWith(
+                        color: Colors.grey,
+                      )),
+              if (item.titleEn != null)
+                Text(item.titleEn!,
+                    style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                          color: Colors.grey,
+                        )),
+            ],
+          ),
+        ),
+        if (item.evidenceStrength != null)
+          Padding(
+            padding: const EdgeInsets.only(left: 8),
+            child: Text('근거: ${item.evidenceStrength!}',
+                style: Theme.of(context).textTheme.bodySmall),
+          ),
+      ],
+    );
+  }
+}
+
+class _References extends ConsumerWidget {
+  const _References({required this.referenceIds});
+  final List<String> referenceIds;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    if (referenceIds.isEmpty) return const SizedBox.shrink();
+    final refsAsync = ref.watch(referencesByIdsProvider(referenceIds));
+    return refsAsync.when(
+      loading: () => const SizedBox.shrink(),
+      error: (_, _) => const SizedBox.shrink(),
+      data: (refs) {
+        if (refs.isEmpty) return const SizedBox.shrink();
+        return Column(
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            Text('참고 (${refs.length})',
+                style: Theme.of(context).textTheme.titleSmall),
+            const SizedBox(height: 8),
+            for (final r in refs) ReferenceExpandCard(reference: r),
+          ],
+        );
+      },
+    );
+  }
+}
+
+class _ImportFooter extends StatelessWidget {
+  const _ImportFooter();
+
+  @override
+  Widget build(BuildContext context) {
+    return SafeArea(
+      child: Padding(
+        padding: const EdgeInsets.all(16),
+        child: Tooltip(
+          message: '다음 업데이트 예정',
+          child: FilledButton.icon(
+            onPressed: null,
+            icon: const Icon(Icons.add_task),
+            label: const Text('내 습관으로 (다음 업데이트 예정)'),
+          ),
+        ),
+      ),
+    );
+  }
+}