Add the desktop "Export settings…" surface for the qbzd daemon epic (T18):
a Developer-settings row that opens a modal with the single default-off
"Include Qobuz login and integration tokens" gate, its warning line, and a
Cancel/Export footer. Confirm() is a Rust callback (wired next). New
SettingsExportState/SettingsExportActions globals, exported from app.slint
so the Rust layer binds them, and the modal mounted in AppShell. New strings
translated across all 8 locales (en es de fr pt ru ja nl).
cc
