bug(gui-client/windows): When you sign out, the IPC service should deactivate DNS

[ReactorScram]

Temporary workaround: Close the GUI. This will cause the IPC service to deactivate DNS control

This doesn't affect Linux because systemd always deactivates DNS for us when the tunnel interface goes down.

Describe the bug

This is a regression from #5704. Originally, we deactivated DNS control when the IPC client disconnected, since that was the same as stopping connlib.

This bug makes it impossible to sign out and back in without manually reverting DNS control, since the portal domain will not resolve

To Reproduce

1. Start the IPC service
2. Sign in to the GUI
3. Sign out from the GUI
4. Try to sign in again, or use curl on any site. The portal will be inaccessible

Expected behavior

Expected the IPC service to deactivate DNS control whenever connlib stops

Screenshots / Logs

Expected:

connlib exited gracefully
Deactivated DNS control
IPC client disconnected

Actual:

connlib exited gracefully
IPC client disconnected
Deactivated DNS control

Platform (please complete the following information)

• Component (i.e. macOS client / Linux client / Gateway / Admin portal): GUI Client
• Firezone Version (e.g. 1.0.0 or N/A): main
• OS and version: (e.g. Ubuntu 22.04 or N/A): Windows, maybe Linux
• Deployment method: (e.g. Docker / Systemd / App Store or N/A): Built from source

Additional context

N/A