Refine: make synchronous pref writes opt-in via sync parameter

Only use commit() (sync disk write) for preferences that opt in with
sync=true. The language preference in OtherConfig is currently the only
one that needs this — it triggers an immediate process restart via
context.restart().

Other string preferences continue using apply() (async) to avoid
unnecessary main-thread blocking.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/main/java/io/legado/app/ui/config/PrefDelegate.kt

@@ -35,6 +35,7 @@ fun <T> prefDelegate(
     key: String,
     defaultValue: T,
     lifecycleOwner: LifecycleOwner? = null,
+    sync: Boolean = false,
     onValueChange: ((T) -> Unit)? = null
 ): PrefDelegate<T> {
     return object : PrefDelegate<T>, SharedPreferences.OnSharedPreferenceChangeListener, DefaultLifecycleObserver {
@@ -85,7 +86,7 @@ fun <T> prefDelegate(
         override fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
             if (_value.value != value) {
                 when (value) {
-                    is String? -> appCtx.putPrefStringSync(key, value)
+                    is String? -> if (sync) appCtx.putPrefStringSync(key, value) else appCtx.putPrefString(key, value)
                     is Int -> appCtx.putPrefInt(key, value)
                     is Boolean -> appCtx.putPrefBoolean(key, value)
                     is Long -> appCtx.putPrefLong(key, value)
@@ -112,8 +113,9 @@ fun <T> prefStateDelegate(
     key: String,
     defaultValue: T,
     lifecycleOwner: LifecycleOwner? = null,
+    sync: Boolean = false,
     onValueChange: ((T) -> Unit)? = null
 ): PrefStateDelegate<T> {
-    val delegate = prefDelegate(key, defaultValue, lifecycleOwner, onValueChange)
+    val delegate = prefDelegate(key, defaultValue, lifecycleOwner, sync, onValueChange)
     return PrefStateDelegate(delegate)
 }

app/src/main/java/io/legado/app/ui/config/otherConfig/OtherConfig.kt

@@ -8,7 +8,8 @@ object OtherConfig {
 
     var language by prefDelegate(
         PreferKey.language,
-        "auto"
+        "auto",
+        sync = true
     )
 
     var updateToVariant by prefDelegate(