Don't flash previous app content when resuming app & auto sign-in is off (#585)

## Description
When the app is put into the background with auto sign-in disabled, it
will remove the current page and show a loading indicator. This way when
the app is resumed, the previous content won't flash on screen for a
split second.

The above should technically fix #584 on its own, but as additional safe
guide, this PR also makes sure the `ApiClient` is configured before
trying to create image URLs.

### Related issues
Fixes #584

app/src/main/java/com/github/damontecres/wholphin/MainActivity.kt

@@ -13,13 +13,16 @@ import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.RectangleShape
 import androidx.compose.ui.unit.dp
 import androidx.datastore.core.DataStore
 import androidx.lifecycle.ViewModel
+import androidx.lifecycle.compose.LifecycleStartEffect
 import androidx.lifecycle.lifecycleScope
 import androidx.lifecycle.viewModelScope
 import androidx.lifecycle.viewmodel.navigation3.rememberViewModelStoreNavEntryDecorator
@@ -208,13 +211,35 @@ class MainActivity : AppCompatActivity() {
                                                         remember(appPreferences) {
                                                             UserPreferences(appPreferences)
                                                         }
-                                                    ApplicationContent(
+                                                    var showContent by remember {
-                                                        user = current.user,
+                                                        mutableStateOf(true)
-                                                        server = current.server,
+                                                    }
-                                                        navigationManager = navigationManager,
+                                                    if (!preferences.appPreferences.signInAutomatically) {
-                                                        preferences = preferences,
+                                                        LifecycleStartEffect(Unit) {
-                                                        modifier = Modifier.fillMaxSize(),
+                                                            onStopOrDispose {
-                                                    )
+                                                                showContent = false
+                                                            }
+                                                        }
+                                                    }
+                                                    if (showContent) {
+                                                        ApplicationContent(
+                                                            user = current.user,
+                                                            server = current.server,
+                                                            navigationManager = navigationManager,
+                                                            preferences = preferences,
+                                                            modifier = Modifier.fillMaxSize(),
+                                                        )
+                                                    } else {
+                                                        Box(
+                                                            modifier = Modifier.size(200.dp),
+                                                            contentAlignment = Alignment.Center,
+                                                        ) {
+                                                            CircularProgressIndicator(
+                                                                color = MaterialTheme.colorScheme.border,
+                                                                modifier = Modifier.align(Alignment.Center),
+                                                            )
+                                                        }
+                                                    }
                                                 }
                                             }
                                         }

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

@@ -242,7 +242,6 @@ class ServerRepository
         }
 
         suspend fun switchServerOrUser() {
-            apiClient.update(baseUrl = null, accessToken = null)
             userPreferencesDataStore.updateData {
                 it
                     .toBuilder()

app/src/main/java/com/github/damontecres/wholphin/services/ImageUrlService.kt

@@ -31,7 +31,7 @@ class ImageUrlService
             imageType: ImageType,
             fillWidth: Int? = null,
             fillHeight: Int? = null,
-        ): String =
+        ): String? =
             when (imageType) {
                 ImageType.BACKDROP,
                 ImageType.LOGO,
@@ -124,8 +124,9 @@ class ImageUrlService
             backgroundColor: String? = null,
             foregroundLayer: String? = null,
             imageIndex: Int? = null,
-        ): String =
+        ): String? {
-            api.imageApi.getItemImageUrl(
+            if (api.baseUrl.isNullOrBlank()) return null
+            return api.imageApi.getItemImageUrl(
                 itemId = itemId,
                 imageType = imageType,
                 maxWidth = maxWidth,
@@ -144,6 +145,7 @@ class ImageUrlService
                 foregroundLayer = foregroundLayer,
                 imageIndex = imageIndex,
             )
+        }
 
         fun getUserImageUrl(userId: UUID) = api.imageApi.getUserImageUrl(userId)
 

app/src/main/java/com/github/damontecres/wholphin/ui/components/GenreCardGrid.kt

@@ -103,7 +103,7 @@ class GenreViewModel
                     loading.value = LoadingState.Success
                 }
 //                val excludeItemIds = mutableSetOf<UUID>()
-                val genreToUrl = ConcurrentHashMap<UUID, String>()
+                val genreToUrl = ConcurrentHashMap<UUID, String?>()
                 val semaphore = Semaphore(4)
                 genres
                     .map { genre ->