Docs: NavBar preview is too short for its dropdown and mobile menu #46

Problem

The NavBar docs preview (<PreviewComponents registryName="navbar" fullBleed>) is only as tall as the bar itself. fullBleed renders the demo with no padding or minimum height (src/components/docs/preview-shell.tsx), so the language dropdown and the mobile menu have no room inside the card:

• On main, the card clips with overflow-hidden, so the open dropdown is cut off at the card edge.
• With the clipping removed (as feat(a11y): keyboard navigation for listbox popups (LanguageSwitcher, PhoneInput, NavBar) #44 does), the dropdown spills out of the card over the Installation section below.

Either way, the preview doesn't show the component's main interaction.

Expected

The NavBar preview stage reserves enough space for its popups: the open language menu with all demo locales, and the mobile menu at narrow widths. Both should fit inside the card.

Suggested fix

• Give the fullBleed stage a minimum height, or let PreviewComponents accept a minHeight / className for the stage, and set it on the NavBar page (roughly min-h-[22rem]).
• Leave the bar at the top of the stage; the empty area below is where the menus open.
• Check the other fullBleed previews aren't affected.

Acceptance

• Open language dropdown fits fully inside the preview card on desktop.
• Mobile menu (~390px) fits inside the card.
• No horizontal page overflow at 390px.
• Screenshots: desktop and ~390px, light and dark.