Quackback suggestion should honor application color theme

The widget's actual light/dark rendering is controlled from the vendor's own workspace admin console, not the embedding page: Admin → Settings → Branding → Theme Mode, with three states — "User choice (allow toggle)", "Light only", "Dark only" (https://quackback.io/docs/admin/branding, "Theme Mode" section). This is a static, per-workspace setting stored server-side and rendered inside the widget's own iframe.

Our SPA has no channel to pass its data-theme attribute into that iframe: the SDK command surface simply does not expose it.

Widget theming should be controlled programmatically by the hosting application, not hard-coded by the admin page.