UI и View Model для поиска диалогов

[KriseevM]

resolves #547
resolves #546

[Namxobick]

Как тебе такое?

suggestionsBuilder: (context, controller) async {
  final suggService = Injector.appInstance.get<DialogSearchService>();

  if (controller.text.length < 3) {
    final history = await suggService.getHistory();
    return [
      for (final e in history ?? const <PreviewDialog>[])
        if (e.title.contains(controller.text))
          searchItemTile(context, e, controller, model),
    ];
  }

  final results = await suggService.search(controller.text);
  return [
    for (final e in results ?? const <PreviewDialog>[])
      searchItemTile(context, e, controller, model),
  ];
},