Show offline notification

Problem

Currently, when the user goes offline, there’s no clear indication in the UI. This creates confusion: users may think ABLE is broken or their actions are not working, when in fact the issue is connectivity.

Expected

• Show a toast notification when the app detects offline status (e.g., “You’re offline.”).

• Toast should auto-dismiss when the connection is back online (or show a brief “Back online” confirmation).