fix(control): use DNS handoff when choosing dial target

[Zhanfg]

Background

During DNS controller handoff, ChooseDialTarget() could still consult the old c.dnsController directly instead of the controller currently active through the handoff mechanism.

If DNS knowledge exists only in the handoff controller, the old lookup misses it and the dial target can incorrectly remain an IP address instead of switching back to the original domain.

This change uses ActiveDnsController() and handles the nil case before consulting DNS knowledge.

A regression test reproduces the handoff state and verifies that the domain is selected and rerouting is requested.

Checklist

• The Pull Request has been fully tested
• There's an entry in the CHANGELOGS
• There is a user-facing docs PR against https://github.com/daeuniverse/dae

Full Changelogs

• Use the active DNS handoff controller when deciding whether a dial target should use its original domain.
• Add a regression test covering DNS knowledge stored in the handoff controller.

Issue Reference

Closes #1054.

Test Result

• Added TestChooseDialTargetUsesDNSHandoff.
• Fork CI for the corrected regression fixture passed.
• Upstream CI is awaiting maintainer approval for fork-originated workflows.