feat: scaffold codespace backend

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

internal/api/errors.go

@@ -0,0 +1,42 @@
+package api
+
+import (
+	"net/http"
+
+	"codespace/internal/util"
+	"codespace/pkg/response"
+
+	"github.com/gin-gonic/gin"
+)
+
+// writeError maps a service-layer error to an HTTP JSON error response.
+func writeError(c *gin.Context, err error) {
+	code := util.CodeOf(err)
+	var status int
+	switch code {
+	case util.CodeBadRequest:
+		status = http.StatusBadRequest
+	case util.CodeNotFound:
+		status = http.StatusNotFound
+	case util.CodeConflict:
+		status = http.StatusConflict
+	default:
+		status = http.StatusInternalServerError
+	}
+	msg := http.StatusText(status)
+	if err != nil {
+		msg = err.Error()
+	}
+	c.JSON(status, response.ErrorBody{Error: response.ErrorDetail{
+		Code:    string(code),
+		Message: msg,
+	}})
+}
+
+// writeBadRequest is a shorthand for 400 responses without a service error.
+func writeBadRequest(c *gin.Context, message string) {
+	c.JSON(http.StatusBadRequest, response.ErrorBody{Error: response.ErrorDetail{
+		Code:    string(util.CodeBadRequest),
+		Message: message,
+	}})
+}