Fix empty host selection state

[kopertop]

Summary

Fixes an empty-state bug where saving a host persists it locally but leaves Hermes Desktop without an active host selection.

Root Cause

AppState.saveConnection(_:) saved the profile but did not promote it to activeConnectionID or persist it as lastConnectionID when the app had no active host.

On launch, AppState also trusted lastConnectionID directly, so a missing or stale preference could strand valid saved hosts in connections.json.

Changes

• Select and persist the saved host when saving from a no-active-host state.
• Recover at startup from missing or stale lastConnectionID by selecting the most recently connected/updated saved host.
• Add regression tests for first-host save, adding additional hosts without switching, missing last-connection preference, and stale last-connection preference.
• Add localization for the new host-saved status message.

Validation

• ./scripts/run-tests.sh passed with 116 tests.

Co-authored by Codex