Implement Metro dependency injection

Metro is a familiar dependency injection library for Block Android engineers because it is heavily inspired by Dagger and Anvil - we've officially endorsed it as as the next thing to migrate to, https://github.com/square/anvil/issues/1149

We should also implement a dependency injection strategy early before the app grows to ease the burden of managing dependencies and increase testability.

Research Metro dependency injection library and its integration with Swift. Look at existing dependency injection patterns in the codebase. Determine where to set up the DI container and how to register dependencies. Verify the implementation by writing tests to ensure dependencies are correctly injected.

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