Screensaver fixes (#1047)

## Description
Fixes a few issues with the in-app & OS screensavers

- Make sure clock is updating for in-app screensaver
- Fix crash if app is force quit before the OS screensaver starts

### Related issues
Fixes #1045 

### Testing
NVIDIA shield

## Screenshots
N/A

## AI or LLM usage
None

app/src/main/java/com/github/damontecres/wholphin/ui/preferences/PreferencesContent.kt

@@ -153,7 +153,7 @@ fun PreferencesContent(
             try {
                 System.loadLibrary("mpv")
                 System.loadLibrary("player")
-            } catch (ex: Exception) {
+            } catch (ex: UnsatisfiedLinkError) {
                 Timber.w(ex, "Could not load libmpv")
                 showToast(context, "MPV is not supported on this device")
                 viewModel.preferenceDataStore.updateData {

app/src/main/java/com/github/damontecres/wholphin/ui/util/LocalClock.kt

@@ -34,7 +34,7 @@ data class Clock(
 fun ProvideLocalClock(content: @Composable () -> Unit) {
     val clock = remember { Clock() }
     LaunchedEffect(Unit) {
-        withContext(Dispatchers.IO) {
+        withContext(Dispatchers.Default) {
             while (isActive) {
                 val now = LocalDateTime.now()
                 val time = TimeFormatter.format(now)