android/src/main: show exit node information in the permanent notification

[jakubmeysner]

Displays exit node status (including the name of the exit node) in the permanent connection notification's content (moving the overall connected/disconnected status to the title).

Fixes tailscale/tailscale#14438

Using exit node	Not using exit node	Disconnected

Could potentially also be extended to modify the notification icon similarly to desktop - however I do not have access to that asset, and it'd probably require some modification to fit within the safe display area.

Also includes formatting of existing code using ktfmt (ktfmtFormat Gradle task) and a fix for an invalid instruction in the Dockerfile causing build failures.

[ghost]

Pull Request Revisions

Revision	Description
r2	Refactored notification and exit node logic Added distinctUntilChanged() to flow, created helper method showForegroundNotification(), and improved exit node name retrieval logic
r1	Added exit node name to notifications Modified notification generation to include the name of the active exit node when one is selected, enhancing the status notification with more contextual information about the current VPN connection.

✅ AI review completed for r2

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[jakubmeysner]

Hi @kari-ts and @nickoneill, sorry about the mention(s), but could you please take a look at this PR when you have a chance?

[kari-ts]

Thanks for the fix!