Current topic: "Issue #54: Codebase Research"
Topic summary: I am researching the files mentioned in the action plan: `ServiceBookApplication.kt`, `BillingManagerImpl.kt`, `SettingsViewModel.kt`, `VehicleListViewModel.kt`, and `MainActivity.kt`. This will help me draft a detailed implementation plan.

Strategic Intent: Examine the codebase files mentioned in the issue to determine the necessary changes for the plan.