Fix taiji fish eyes and expose theme toggle on mobile.

Correct yin-yang eye colors with contrast strokes, and show light/dark switch in mobile header with Chinese labels.

Co-authored-by: Cursor <cursoragent@cursor.com>

components/header.tsx

@@ -36,19 +36,21 @@ function NavLink({ href, label }: { href: string; label: string }) {
 export default function Header() {
   return (
     <header className="relative z-10 border-b border-border/40 bg-card/70 py-3 shadow-sm backdrop-blur-md">
-      <div className={`${APP_CONTAINER} flex flex-col gap-2 sm:flex-row sm:items-center sm:justify-between`}>
-        <Link href="/" className="flex items-center justify-center gap-2 sm:justify-start">
+      <div
+        className={`${APP_CONTAINER} grid grid-cols-[1fr_auto] items-center gap-y-2 sm:flex sm:justify-between`}
+      >
+        <Link href="/" className="flex items-center gap-2">
           <TaijiIcon />
           <span className="font-medium tracking-wide">知命阁</span>
         </Link>
-        <nav className="flex flex-wrap items-center justify-center gap-x-4 gap-y-1">
+        <div className="justify-self-end sm:order-last">
+          <ModeToggle />
+        </div>
+        <nav className="col-span-2 flex flex-wrap items-center justify-center gap-x-4 gap-y-1 sm:order-none sm:col-span-1 sm:flex-1">
           {NAV_ITEMS.map((item) => (
             <NavLink key={item.href} {...item} />
           ))}
         </nav>
-        <div className="flex justify-center sm:justify-end">
-          <ModeToggle />
-        </div>
       </div>
     </header>
   );