refactor: simplify homepage layout, consolidate landing page components

Merge hero/stats/features/footer sections into home-page-content.tsx,
remove separate landing-page.tsx. Update styles, layout, navbar, and
backend config.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/src/lib/auth.ts

@@ -28,7 +28,7 @@ export const authOptions: NextAuthOptions = {
           const { username, password } = validatedFields.data;
 
           // 调用后端API进行认证
-          const response = await fetch(`${process.env.NEXT_PUBLIC_API_URL}/auth/login`, {
+          const response = await fetch(`${process.env.BACKEND_INTERNAL_URL || 'http://127.0.0.1:8000'}/auth/login`, {
             method: "POST",
             headers: {
               "Content-Type": "application/json",