feat(update): add setup fallback action and bump 2.1.2

- add installer asset detection in update service

- add 'Download and install (setup)' action in update dialog

- bump app version to 2.1.2 and extend update service test

main.py

@@ -407,6 +407,10 @@ class VkChatManager(QMainWindow):
             )
             update_now_button = message_box.addButton("Обновить сейчас", QMessageBox.ButtonRole.AcceptRole)
             download_button = message_box.addButton("Скачать", QMessageBox.ButtonRole.AcceptRole)
+            setup_button = None
+            installer_url = result.get("installer_url")
+            if installer_url:
+                setup_button = message_box.addButton("Скачать и установить (setup)", QMessageBox.ButtonRole.AcceptRole)
             releases_button = message_box.addButton("Релизы", QMessageBox.ButtonRole.ActionRole)
             cancel_button = message_box.addButton("Позже", QMessageBox.ButtonRole.RejectRole)
             message_box.setDefaultButton(update_now_button)
@@ -422,6 +426,9 @@ class VkChatManager(QMainWindow):
                     if release_url:
                         QDesktopServices.openUrl(QUrl(release_url))
                 return
+            if setup_button is not None and clicked is setup_button and installer_url:
+                QDesktopServices.openUrl(QUrl(installer_url))
+                return
             if clicked is download_button and download_url:
                 QDesktopServices.openUrl(QUrl(download_url))
             elif clicked in (download_button, releases_button) and release_url: