Implement runtime notification permission; bump targetSdk to 33

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/reminders/ReminderScheduler.kt

@@ -115,6 +115,11 @@ class ReminderScheduler @Inject constructor(
         for (habit in reminderHabits) schedule(habit)
     }
 
+    @Synchronized
+    fun hasHabitsWithReminders(): Boolean {
+        return !habitList.getFiltered(HabitMatcher.WITH_ALARM).isEmpty
+    }
+
     @Synchronized
     fun startListening() {
         commandRunner.addListener(this)