feat: setup barrelsby for automatic barrel file generation

Add barrelsby as a dev dependency with a `generate-barrels` npm script and a `barrelesby.json` config targeting `./src`. This automates creation of barrel/index files to simplify imports across the project.

src/data/models/metrics/index.ts

@@ -0,0 +1,3 @@
+// metrics 子目录 barrel export
+export { AppEvent } from "./app_event";
+export { PwaEvent } from "./pwa_event";