feat(lyra)!: 接入分类查询并集中组装依赖

- 使用 Squirrel 与 sqlx 实现分类查询
- 集中组装依赖并向 handler 注入 model 接口
- 显式转换分类响应 DTO，统一空列表输出
- 补充路由与 handler 测试，同步架构文档

BREAKING CHANGE: 将 GET /hello 替换为 GET /test，响应由问候字符串改为分类列表

go/projects/lyra/internal/handler/hello.go

@@ -1,13 +0,0 @@
-package handler
-
-import (
-	"lyra/internal/httpx"
-
-	"github.com/gin-gonic/gin"
-)
-
-func Hello() gin.HandlerFunc {
-	return func(c *gin.Context) {
-		httpx.OK(c, "Hello, World!")
-	}
-}

go/projects/lyra/internal/handler/test.go

@@ -0,0 +1,43 @@
+package handler
+
+import (
+	"lyra/internal/api"
+	"lyra/internal/httpx"
+	"lyra/internal/model"
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+)
+
+type TestHandler struct {
+	categoryModel model.CategoryModel
+}
+
+func NewTestHandler(categoryModel model.CategoryModel) *TestHandler {
+	return &TestHandler{categoryModel: categoryModel}
+}
+
+func (h *TestHandler) Hello() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		categories, err := h.categoryModel.FindAll(c.Request.Context())
+		if err != nil {
+			httpx.Fail(c, http.StatusInternalServerError, api.CodeInternalError, "获取分类列表失败")
+			return
+		}
+		httpx.OK(c, toCategoryResponses(categories))
+	}
+}
+
+// toCategoryResponses 显式把内部模型转换为响应 DTO；make 保证空结果输出 data:[] 而非 null。
+func toCategoryResponses(categories []*model.Category) []api.CategoryResponse {
+	responses := make([]api.CategoryResponse, 0, len(categories))
+	for _, category := range categories {
+		responses = append(responses, api.CategoryResponse{
+			ID:    category.ID,
+			Slug:  category.Slug,
+			Title: category.Title,
+			Sort:  category.Sort,
+		})
+	}
+	return responses
+}

go/projects/lyra/internal/handler/test_test.go

@@ -0,0 +1,128 @@
+package handler_test
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"lyra/internal/handler"
+	"lyra/internal/model"
+
+	"github.com/gin-gonic/gin"
+)
+
+type fakeCategoryModel struct {
+	categories []*model.Category
+	err        error
+	calls      int
+	gotCtx     context.Context
+}
+
+func (f *fakeCategoryModel) FindAll(ctx context.Context) ([]*model.Category, error) {
+	f.calls++
+	f.gotCtx = ctx
+	return f.categories, f.err
+}
+
+func serveHello(t *testing.T, fake *fakeCategoryModel, req *http.Request) *httptest.ResponseRecorder {
+	t.Helper()
+	gin.SetMode(gin.TestMode)
+	engine := gin.New()
+	engine.GET("/test", handler.NewTestHandler(fake).Hello())
+	recorder := httptest.NewRecorder()
+	engine.ServeHTTP(recorder, req)
+	return recorder
+}
+
+func newHelloRequest() *http.Request {
+	return httptest.NewRequest(http.MethodGet, "/test", nil)
+}
+
+func TestHelloMapsCategoriesToResponse(t *testing.T) {
+	fake := &fakeCategoryModel{categories: []*model.Category{
+		{ID: 1, Slug: "go-basics", Title: "Go 基础", Sort: 1},
+		{ID: 2, Slug: "sql-practice", Title: "SQL 练习", Sort: 2},
+	}}
+
+	recorder := serveHello(t, fake, newHelloRequest())
+
+	if fake.calls != 1 {
+		t.Fatalf("模型调用次数 = %d, want 1", fake.calls)
+	}
+	if recorder.Code != http.StatusOK {
+		t.Fatalf("status = %d, want %d", recorder.Code, http.StatusOK)
+	}
+	want := `{"success":true,"data":[{"id":1,"slug":"go-basics","title":"Go 基础","sort":1},{"id":2,"slug":"sql-practice","title":"SQL 练习","sort":2}]}`
+	if got := recorder.Body.String(); got != want {
+		t.Fatalf("body = %q, want %q", got, want)
+	}
+}
+
+func TestHelloReturnsEmptyArrayForNoCategories(t *testing.T) {
+	tests := []struct {
+		name       string
+		categories []*model.Category
+	}{
+		{name: "空切片", categories: []*model.Category{}},
+		{name: "nil结果", categories: nil},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fake := &fakeCategoryModel{categories: tt.categories}
+
+			recorder := serveHello(t, fake, newHelloRequest())
+
+			if fake.calls != 1 {
+				t.Fatalf("模型调用次数 = %d, want 1", fake.calls)
+			}
+			if recorder.Code != http.StatusOK {
+				t.Fatalf("status = %d, want %d", recorder.Code, http.StatusOK)
+			}
+			want := `{"success":true,"data":[]}`
+			if got := recorder.Body.String(); got != want {
+				t.Fatalf("body = %q, want %q", got, want)
+			}
+		})
+	}
+}
+
+func TestHelloReturnsInternalErrorOnModelFailure(t *testing.T) {
+	modelErr := errors.New("数据库连接被拒绝: 10.0.0.8:5432")
+	fake := &fakeCategoryModel{err: modelErr}
+
+	recorder := serveHello(t, fake, newHelloRequest())
+
+	if fake.calls != 1 {
+		t.Fatalf("模型调用次数 = %d, want 1", fake.calls)
+	}
+	if recorder.Code != http.StatusInternalServerError {
+		t.Fatalf("status = %d, want %d", recorder.Code, http.StatusInternalServerError)
+	}
+	want := `{"success":false,"error":{"code":10002,"message":"获取分类列表失败"}}`
+	if got := recorder.Body.String(); got != want {
+		t.Fatalf("body = %q, want %q", got, want)
+	}
+	if strings.Contains(recorder.Body.String(), modelErr.Error()) {
+		t.Fatalf("响应泄漏了内部错误信息: %q", recorder.Body.String())
+	}
+}
+
+type contextKey struct{}
+
+func TestHelloPassesRequestContextToModel(t *testing.T) {
+	fake := &fakeCategoryModel{categories: []*model.Category{}}
+	reqCtx := context.WithValue(context.Background(), contextKey{}, "req-42")
+	req := newHelloRequest().WithContext(reqCtx)
+
+	serveHello(t, fake, req)
+
+	if fake.gotCtx != reqCtx {
+		t.Fatalf("模型收到非请求 context: %v", fake.gotCtx)
+	}
+	if got, _ := fake.gotCtx.Value(contextKey{}).(string); got != "req-42" {
+		t.Fatalf("context 值 = %q, want %q", got, "req-42")
+	}
+}