Redesign LanguageSwitcher #59

Bring LanguageSwitcher to shadcn-registry quality. Depends on #58.

• shadcn tokens; trigger variant (outline / ghost / secondary) and size.
• Animated enter/exit menu (reduced motion respected), flips upward when there's no room below, align / side.
• Search row with icon, clear button and empty state; quieter selected state.
• Customisation: classNames slots, renderOption, showCode, searchable, searchPlaceholder, emptyMessage, disabled.
• Backward compatible; keyboard and ARIA behaviour unchanged.