Ports the desktop user-settings screens from the Settings Redesign Figma (TFhrx7FBh2Ue5SGH8CUeBU) onto a shared set of primitives: a sidebar Navigation matching the DS component's four Active x Hovered states, plus header/toolbar/list/row/entry pieces and a drill-down shell for the in-place sub-views. Seven tabs and nine drill-downs. Keys keeps its existing `tangled.publicKey` wiring and moves the add form from a popover to /settings/keys/new; the rest are mocked, since nothing behind them exists yet. Three token pairs are new because the navigation aliases *invert* between modes -- light recesses the frame and raises the active item, dark does the opposite -- so they cannot be spelled with an existing pair. Button gains per-variant disabled surfaces: Figma models disabled as its own fill/text pair rather than a dimmed enabled state, which is what the disabled Save and Add buttons in the designs need. Tag grows the DS badge geometry as an additive `sm` size plus the status colours, leaving its existing callers untouched. Verified light and dark against the Figma renders; nav, card and surface tokens plus nav/card geometry and heading size all match. Refs TAN-575. Signed-off-by: eti <eti@eti.tf>