feat(settings): add desktop API endpoint configuration

[JnyRoad]

Summary

Adds a desktop Network and API settings card that shows the active same-machine API Base URL and saves validated next-launch listener settings without exposing account API keys.

Features

• Adds administrator-only APIs to read and save network listener settings.
• Supports local, LAN, and externally published next-launch modes with validated listener ports and public origins.
• Shows the API Base URL currently used by the desktop service and provides an explicit copy action.
• Persists next-launch choices separately from the running listener; port and access-scope changes take effect only after a full desktop restart.
• Keeps browser-runtime display and listener configuration paired so the shown endpoint matches the active runtime.

Implementation

• Adds the runtime network configuration module and packages it with the desktop backend.
• Updates the runtime settings UI, type contract, desktop launcher, backend documentation, and focused regression coverage.

Validation

• Python: 57 targeted network, launcher, and API-setting tests passed.
• Frontend: RuntimeSettingsPage tests passed.
• Frontend production build passed.