Add login-page site gate and refresh marketing site for complex-care positioning.

Replace HTTP Basic Auth with a branded /login flow and signed session cookie, using Next.js 16's proxy convention for route protection.

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

src/app/(marketing)/layout.tsx

@@ -0,0 +1,16 @@
+import { ScreenBackground } from "~/components/screen-background";
+import { SiteFooter } from "~/components/site-footer";
+import { SiteHeader } from "~/components/site-header";
+
+export default function MarketingLayout({
+  children,
+}: Readonly<{ children: React.ReactNode }>) {
+  return (
+    <>
+      <ScreenBackground />
+      <SiteHeader />
+      <main>{children}</main>
+      <SiteFooter />
+    </>
+  );
+}