style(ui): adjust primitives, card shadow and header nav

components/header.tsx

@@ -100,20 +100,20 @@ export function Header() {
           </Link>
 
           <nav className="hidden md:flex items-center gap-1">
-            {navLinks.map((link) => (
-              <Link
-                key={link.href}
-                href={link.href}
-                className={cn(
-                  "rounded-lg px-4 py-2 text-sm font-medium transition-colors",
-                  pathname === link.href || (link.href !== "/" && pathname.startsWith(link.href))
-                    ? "bg-secondary text-foreground"
-                    : "text-muted-foreground hover:bg-secondary/60 hover:text-foreground",
-                )}
-              >
-                {link.label}
-              </Link>
-            ))}
+            {navLinks.map((link) => {
+              const isActive =
+                pathname === link.href || (link.href !== "/" && pathname.startsWith(link.href))
+              return (
+                <Button
+                  key={link.href}
+                  variant={isActive ? "secondary" : "ghost"}
+                  className={!isActive ? "text-muted-foreground" : undefined}
+                  asChild
+                >
+                  <Link href={link.href}>{link.label}</Link>
+                </Button>
+              )
+            })}
           </nav>
         </div>
         <div className="flex items-center justify-end gap-1">
@@ -227,11 +227,11 @@ export function Header() {
               </DropdownMenu>
             </>
           ) : (
-            <div className="hidden md:flex items-center gap-2">
-              <Button variant="ghost" size="sm" asChild>
+            <div className="hidden md:flex items-center gap-1">
+              <Button variant="ghost" className="text-muted-foreground" asChild>
                 <Link href="/login">登录</Link>
               </Button>
-              <Button size="sm" asChild>
+              <Button variant="ghost" className="text-muted-foreground" asChild>
                 <Link href="/register">注册</Link>
               </Button>
             </div>