[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/data/seed/seed_importer_test.dart

@@ -7,7 +7,7 @@ const _protocols = '''
 [
   {
     "id": "morning_sunlight",
-    "category": "health",
+    "category": "light_circadian",
     "title": "아침 햇빛",
     "what": "기상 후 햇빛.",
     "when": "기상 후 30~60분.",

app/test/data/seed/test_seeds.dart

@@ -0,0 +1,126 @@
+// Stub seed loader used by both seed_importer_test and catalog_repository_test.
+// 1 row per catalog (minimal but schema-valid).
+
+const protocolsStub = '''
+[
+  {
+    "id": "morning_sunlight",
+    "category": "light_circadian",
+    "title": "아침 햇빛",
+    "what": "기상 후 햇빛.",
+    "when": "기상 후 30~60분.",
+    "dose": "5~10분.",
+    "why": "ipRGC 자극.",
+    "how": ["나간다", "쳐다본다"],
+    "check": "60분 이내 외출",
+    "reference_ids": ["ref_x"],
+    "source_doc": "huberman-protocols.md"
+  }
+]
+''';
+
+const breakProtocolsStub = '''
+[
+  {
+    "id": "alcohol",
+    "category": "alcohol",
+    "title": "음주",
+    "huberman_summary": "ep 86",
+    "phases": [{"week": 1, "what": "환경 정리"}],
+    "default_common_frames": ["dopamine_reset"]
+  }
+]
+''';
+
+const commonFramesStub = '''
+[
+  {
+    "id": "dopamine_reset",
+    "title": "도파민 리셋",
+    "what": "30일 절제",
+    "why": "수용체 회복",
+    "check": "30일 무자극"
+  }
+]
+''';
+
+const methodologiesStub = '''
+[
+  {
+    "id": "atomic_habits",
+    "name": "Atomic Habits",
+    "originator": "James Clear",
+    "one_line_definition": "1% 개선",
+    "core_unit": "1회 행동",
+    "huberman_fit_score": 5,
+    "is_core_engine": true
+  }
+]
+''';
+
+const framePatternsStub = '''
+[
+  {
+    "id": "fp_alcohol",
+    "domain": "drink",
+    "avoidance_keyword": "술 끊기",
+    "l0_example": "술 끊기",
+    "l2_suggestion": "저녁엔 무알콜",
+    "l3_identity": "맑은 정신 추구"
+  }
+]
+''';
+
+const rewardMenuItemsStub = '''
+[
+  {
+    "id": "rmi_walk",
+    "tier_recommended": "T1",
+    "title": "산책 30분"
+  }
+]
+''';
+
+const referencesStub = '''
+[
+  {
+    "id": "ref_x",
+    "kind": "url",
+    "title": "Sample",
+    "url": "https://example.com"
+  }
+]
+''';
+
+const dietPatternsStub = '''
+[
+  {
+    "id": "med",
+    "name": "지중해 식단",
+    "core": "올리브유 + 채소 + 생선 위주의 전통 식단.",
+    "evidence_strength": "strong"
+  }
+]
+''';
+
+Future<String> testStubLoader(String path) async {
+  switch (path) {
+    case 'assets/seed/protocols.json':
+      return protocolsStub;
+    case 'assets/seed/break_protocols.json':
+      return breakProtocolsStub;
+    case 'assets/seed/common_frames.json':
+      return commonFramesStub;
+    case 'assets/seed/methodologies.json':
+      return methodologiesStub;
+    case 'assets/seed/frame_patterns.json':
+      return framePatternsStub;
+    case 'assets/seed/reward_menu_items.json':
+      return rewardMenuItemsStub;
+    case 'assets/seed/references.json':
+      return referencesStub;
+    case 'assets/seed/diet_patterns.json':
+      return dietPatternsStub;
+  }
+  throw StateError('unexpected asset: $path');
+}