Enhancement: Re-use existing restaurant list data when switching between "Discover" and "Favorite" screens.

[huhx0015]

Currently, the restaurant list data is reloaded when switching between "Discover" and "Favorite" options in the navigation drawer.

As this reduces the general flow of the app, we should instead use the display restaurant list data to build the favorites list (and vice-versa). By doing so, we minimize the number of necessary API calls and user flow is less disruptive.