fix: update error code to BadRequestErr in HandleAppStart and add corresponding constant

Author: dido18

internal/api/handlers/app_start.go

@@ -65,9 +65,10 @@ func HandleAppStart(
 		err = app.ValidateBricks(appLoaded.Descriptor, bricksIndex)
 		if err != nil {
 			sseStream.SendError(render.SSEErrorData{
-				Code:    render.InternalServiceErr,
+				Code:    render.BadRequestErr,
 				Message: err.Error(),
 			})
+			return
 		}
 
 		type progress struct {

internal/render/sse.go

@@ -30,6 +30,7 @@ type SSEErrCode string
 
 const (
 	InternalServiceErr SSEErrCode = "INTERNAL_SERVER_ERROR"
+	BadRequestErr      SSEErrCode = "BAD_REQUEST_ERROR"
 )
 
 type SSEErrorData struct {