chore: upgrade i18next 26, prettier 3, fontsource-variable, domhandler 6, lint-staged 17

- i18next 23->26 + react-i18next 15->17
- prettier 2->3, reformat all files
- replace @fontsource/inter with @fontsource-variable/inter 5, update import path
- domhandler 5->6 (aligns with transitive deps)
- lint-staged 16->17

src/app/components/nav/NavItem.tsx

@@ -23,11 +23,11 @@ export const NavItem = as<
 export const NavLink = forwardRef<HTMLAnchorElement, ComponentProps<typeof Link>>(
   ({ className, ...props }, ref) => (
     <Link className={classNames(css.NavLink, className)} {...props} ref={ref} />
-  )
+  ),
 );
 
 export const NavButton = as<'button'>(
   ({ as: AsNavButton = 'button', className, ...props }, ref) => (
     <AsNavButton className={classNames(css.NavLink, className)} {...props} ref={ref} />
-  )
+  ),
 );