Fix Android boot, widget, and reconnect flows

[yappologistic]

Summary

• move VPN widget toggling into a dedicated VpnWidgetToggleReceiver so widget providers only update UI and toggle handling runs through a single Hilt-enabled receiver
• harden boot and reconnect startup paths by using goAsync(), ContextCompat.startForegroundService(...), and foreground-service pending intents where Android expects them
• avoid repeated update checks after failures by saving the last-check timestamp before the network request, disable app backups, and pin Hilt to 2.57.1 to match the current project setup

Details

• BootReceiver now handles only BOOT_COMPLETED, uses the application context, logs failures, and finishes its async work explicitly
• both widget providers now route tap actions through VpnWidgetToggleReceiver, which reconnects/disconnects centrally and opens the app when VPN permission still needs user approval
• reconnect notification actions now create service intents with PendingIntent.getForegroundService(...) on Android O+ so reconnect actions start reliably from notifications

Testing

• ./gradlew :app:compileFullDebugKotlin --console=plain --no-daemon
• ./gradlew :app:compileLiteDebugKotlin --console=plain --no-daemon