feat: localize interview questions (ko/en), send X-Lang header

internal/interview/catalog.go

@@ -2,28 +2,49 @@ package interview
 
 import "tutor/internal/workflows"
 
-func BackendDeveloperQuestions() []Question {
-	return []Question{
+var questionPrompts = map[string]map[string]string{
+	"ko": {
+		"backend-http-idempotency": "HTTP 메서드가 멱등성을 가지려면 어떤 조건이 필요하며, 재시도 시 왜 중요한가요?",
+		"backend-db-index-tradeoff": "데이터베이스 인덱스를 추가하면 API가 어떻게 개선되며, 어떤 트레이드오프가 발생할 수 있나요?",
+		"backend-cache-invalidation": "API 응답을 캐싱할지 어떻게 결정하며, 오래된 데이터는 어떻게 처리하나요?",
+	},
+	"en": {
+		"backend-http-idempotency": "What makes an HTTP method idempotent, and why does that matter for retries?",
+		"backend-db-index-tradeoff": "When would adding a database index improve an API, and what tradeoffs can it introduce?",
+		"backend-cache-invalidation": "How would you decide whether to cache an API response, and how would you handle stale data?",
+	},
+}
+
+func BackendDeveloperQuestions(lang string) []Question {
+	if lang == "" {
+		lang = "en"
+	}
+	base := []Question{
 		{
-			ID:     "backend-http-idempotency",
-			Prompt: "What makes an HTTP method idempotent, and why does that matter for retries?",
+			ID: "backend-http-idempotency",
 			Concepts: []workflows.ConceptRef{
 				{ID: "http-idempotency", Label: "HTTP idempotency", Track: BackendDeveloperTrack},
 			},
 		},
 		{
-			ID:     "backend-db-index-tradeoff",
-			Prompt: "When would adding a database index improve an API, and what tradeoffs can it introduce?",
+			ID: "backend-db-index-tradeoff",
 			Concepts: []workflows.ConceptRef{
 				{ID: "database-indexes", Label: "Database indexes", Track: BackendDeveloperTrack},
 			},
 		},
 		{
-			ID:     "backend-cache-invalidation",
-			Prompt: "How would you decide whether to cache an API response, and how would you handle stale data?",
+			ID: "backend-cache-invalidation",
 			Concepts: []workflows.ConceptRef{
 				{ID: "cache-invalidation", Label: "Cache invalidation", Track: BackendDeveloperTrack},
 			},
 		},
 	}
+	for i := range base {
+		if p, ok := questionPrompts[lang][base[i].ID]; ok {
+			base[i].Prompt = p
+		} else if p, ok := questionPrompts["en"][base[i].ID]; ok {
+			base[i].Prompt = p
+		}
+	}
+	return base
 }

internal/interview/service.go

@@ -44,7 +44,7 @@ func (s *Service) CreateSession(_ context.Context, input CreateSessionInput) (Se
 		TargetRole:        input.TargetRole,
 		Stack:             append([]string(nil), input.Stack...),
 		InterviewTimeline: input.InterviewTimeline,
-		Questions:         BackendDeveloperQuestions(),
+		Questions:         BackendDeveloperQuestions(input.Lang),
 		CreatedAt:         time.Now().UTC(),
 	}
 	if s.memory != nil {

internal/interview/types.go

@@ -47,6 +47,7 @@ type CreateSessionInput struct {
 	TargetRole        string
 	Stack             []string
 	InterviewTimeline string
+	Lang              string
 }
 
 type SubmitAnswerInput struct {