Allow deleting templates

lib/database/collections/recurrent.dart

@@ -15,4 +15,18 @@ class RecurringTransaction {
   final template = IsarLink<TransactionTemplate>();
 
   final account = IsarLink<Account>();
+
+  bool isDue(DateTime now) {
+    if (lastExecution == null) {
+      return true;
+    }
+
+    final expectedNextExecution = lastExecution!.add(Duration(days: days));
+    if (now.isAfter(expectedNextExecution)) {
+      return true;
+    }
+
+    return now.difference(expectedNextExecution).inDays.abs() <=
+        (days * 0.5).toInt();
+  }
 }