Manual-only new chapters check option

app/src/main/kotlin/org/koitharu/kotatsu/tracker/work/TrackWorker.kt

@@ -245,10 +245,13 @@ class TrackWorker @AssistedInject constructor(
 	) : PeriodicWorkScheduler {
 
 		override suspend fun schedule() {
+			val frequency = settings.trackerFrequencyFactor
+			if (frequency <= 0f) {
+				return unschedule()
+			}
 			val constraints = createConstraints()
 			val runCount = dbProvider.get().getTracksDao().getTracksCount()
 			val runsPerFullCheck = (runCount / BATCH_SIZE.toFloat()).toIntUp().coerceAtLeast(1)
-			val frequency = settings.trackerFrequencyFactor
 			val interval = (18 / runsPerFullCheck / frequency).roundToInt().coerceAtLeast(2)
 			val request = PeriodicWorkRequestBuilder<TrackWorker>(interval.toLong(), TimeUnit.HOURS)
 				.setConstraints(constraints)

app/src/main/res/values/arrays.xml

@@ -93,6 +93,7 @@
 		<item>@string/multiple_cbz_files</item>
 	</string-array>
 	<string-array name="tracker_frequency" translatable="false">
+		<item>@string/manual</item>
 		<item>@string/less_frequently</item>
 		<item>@string/system_default</item>
 		<item>@string/more_frequently</item>

app/src/main/res/values/constants.xml

@@ -64,6 +64,7 @@
 		<item>2</item>
 	</string-array>
 	<string-array name="values_tracker_frequency" translatable="false">
+		<item>-1</item>
 		<item>0.4</item>
 		<item>1</item>
 		<item>2</item>