[Feature] When the connection is lost, show an error message

[SchaffRita]

When the connection is lost in the desktop app with the LifeUp Cloud on mobile, the app does not show any error messages.
The user only sees that suddenly, there is no data displayed in any of the panels.

You have to go into the Settings to check if the connection is lost.

Requirements

• LifeUp Cloud installed and running, connected to the same network
• LifeUp installed
• LifeUp Desktop installed and running, connected to the same network

Steps to Reproduce

1. Open LifeUp Cloud
2. Check the displayed IP address
3. Enter it on LifeUp Desktop
4. Click on Test
5. Assert that you can see all the elements
6. Turn off the internet connection, e.g. by disabling the Wifi adapter or pulling out the LAN cable
7. Check the menu elements (Tasks, Status, Shop, Achi., Feelings, Settings)

✔️ Expected Results
A popup message or the background of the items displays the following error message:
There is no connection to the LifeCloud server.
Please go to the Settings and check if the IP address is correct and if you are connected to the same network.

❌ Actual Results
No items are displayed. There are no error messages advising the user that something is wrong and the general steps that should be taken.