启动时_routeFactory方法多次执行

将FlutterBoostActivity作为启动时入口Activity，导致_routeFactory多次执行
一次是从dart端执行_routeFactory
一次是从原生端跳转路由发生的执行_routeFactory

Start with the FlutterBoostActivity entry point and trace the two _routeFactory invocation paths described in the issue: the Dart-side startup and the native-side route transition. Confirm the startup behavior and identify what should count as the single expected execution before defining the fix and its verification.

Written by the indexing model from the issue text.