Don't include "app state" preferences in backups

core/src/main/java/eu/kanade/tachiyomi/core/security/SecurityPreferences.kt

@@ -1,6 +1,7 @@
 package eu.kanade.tachiyomi.core.security
 
 import eu.kanade.tachiyomi.core.R
+import tachiyomi.core.preference.Preference
 import tachiyomi.core.preference.PreferenceStore
 import tachiyomi.core.preference.getEnum
 
@@ -20,7 +21,10 @@ class SecurityPreferences(
      * For app lock. Will be set when there is a pending timed lock.
      * Otherwise this pref should be deleted.
      */
-    fun lastAppClosed() = preferenceStore.getLong("last_app_closed", 0)
+    fun lastAppClosed() = preferenceStore.getLong(
+        Preference.appStateKey("last_app_closed"),
+        0,
+    )
 
     enum class SecureScreenMode(val titleResId: Int) {
         ALWAYS(R.string.lock_always),

core/src/main/java/tachiyomi/core/preference/Preference.kt

@@ -22,21 +22,29 @@ interface Preference<T> {
 
     fun stateIn(scope: CoroutineScope): StateFlow<T>
 
-    val isPrivate: Boolean
-        get() = key().startsWith(PRIVATE_PREFIX)
-
     companion object {
         /**
-         * A preference that should not be exposed in places like backups.
+         * A preference that should not be exposed in places like backups without user consent.
          */
         fun isPrivate(key: String): Boolean {
             return key.startsWith(PRIVATE_PREFIX)
         }
-
         fun privateKey(key: String): String {
             return "${PRIVATE_PREFIX}$key"
         }
 
+        /**
+         * A preference used for internal app state that isn't really a user preference
+         * and therefore should not be inplaces like backips.
+         */
+        fun isAppState(key: String): Boolean {
+            return key.startsWith(APP_STATE_PREFIX)
+        }
+        fun appStateKey(key: String): String {
+            return "${APP_STATE_PREFIX}$key"
+        }
+
+        private const val APP_STATE_PREFIX = "__APP_STATE_"
         private const val PRIVATE_PREFIX = "__PRIVATE_"
     }
 }