Fix some IO related crashes (#1008)

## Description
- Catch network exceptions when querying to populate the nav drawer
- Perform screensaver work on IO thread
- Fix possible crash if screensaver service runs while regular activity
is destroyed
- Fix genre images & backdrop images not loading

This PR also adds an Jellyfin SDK `ApiClient` wrapper to push all
network calls onto the IO thread. And tries to use a more strict
network-on-main policy for debug builds.

### Related issues
Fixes #994
Fixes #1001
Should fix #1003

### Testing
Emulator with simulated exception throws

## Screenshots
N/A

## AI or LLM usage
None

app/src/main/java/com/github/damontecres/wholphin/data/ServerRepository.kt

@@ -42,8 +42,6 @@ class ServerRepository
         val apiClient: ApiClient,
         val userPreferencesDataStore: DataStore<AppPreferences>,
     ) {
-        private val sharedPreferences = getServerSharedPreferences(context)
-
         private var _current = EqualityMutableLiveData<CurrentUser?>(null)
         val current: LiveData<CurrentUser?> = _current
 
@@ -107,7 +105,7 @@ class ServerRepository
                     _current.value = CurrentUser(updatedServer, updatedUser)
                     _currentUserDto.value = userDto
                 }
-                sharedPreferences.edit(true) {
+                getServerSharedPreferences(context).edit(true) {
                     putString(SERVER_URL_KEY, updatedServer.url)
                     putString(ACCESS_TOKEN_KEY, updatedUser.accessToken)
                 }