refactor: remove @nextcloud/initial-state@2 usage

[ShGKme]

☑️ Resolves

• Currently, the initial state is used only for notifications app settings (like in the original app)
• App mutates initial state on settings and user status change
• Mutating the initial state is not compatible with the latest @nextcloud/initial-state
• Instead of sharing the state via initial state, computing it on the only place it is actually needed.

For testing:

1. Enable dev mode
2. Open any conversation
3. Use Show Call Popup and listen for the sound depending on settings and user status

[Antreesy]

Tested against stable33