[todo-mvp] Change setLoadingIndicator to two separate functions

According to SOLID principles, a function should have only a single responsibility, but the `setLoadingIndicator()` function has two responsibilities, showing and hiding. I want to break it into two functions such as `showLoadingIndicator()` and `hideLoadingIndicator()`.

Search the repository for setLoadingIndicator() and inspect its callers to understand the existing show and hide behavior. Split those responsibilities into separate showLoadingIndicator() and hideLoadingIndicator() functions, then verify that all callers still produce the expected loading-indicator behavior.

Written by the indexing model from the issue text.