feat(project): migration 0002 + errs codes for project/requirement/issue

internal/infra/errs/errs.go

@@ -27,6 +27,11 @@ const (
 	CodeUpstream     Code = "upstream_error"
 	CodeUnavailable  Code = "unavailable"
 	CodeInternal     Code = "internal"
+
+	// Project 模块专用细粒度 code（HTTP 仍 409，但前端可据此区分提示）。
+	CodeProjectSlugTaken  Code = "project_slug_taken"
+	CodeProjectArchived   Code = "project_archived"
+	CodeRequirementClosed Code = "requirement_closed"
 )
 
 // AppError is the application's structured error type. It carries a stable
@@ -97,7 +102,8 @@ func HTTPStatus(code Code) int {
 		return http.StatusForbidden
 	case CodeNotFound:
 		return http.StatusNotFound
-	case CodeConflict:
+	case CodeConflict,
+		CodeProjectSlugTaken, CodeProjectArchived, CodeRequirementClosed:
 		return http.StatusConflict
 	case CodeRateLimited:
 		return http.StatusTooManyRequests