Support ultrawide layout with equal columns and taiji branding.

Use 50/50 mode workspace columns, widen content to 1920px on fish screens, replace header logo with taiji icon, and add full-page taiji backdrop.

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

app/combined/page.tsx

@@ -1,10 +1,11 @@
 import PageShell from "@/components/page-shell";
 import CombinedForm from "@/components/modes/combined-form";
+import { APP_CONTAINER } from "@/lib/layout";
 
 export default function CombinedPage() {
   return (
     <PageShell>
-      <div className="border-b border-border/40 px-4 py-6 text-center">
+      <div className={`${APP_CONTAINER} border-b border-border/40 py-6 text-center`}>
         <h1 className="text-2xl font-bold tracking-wide">综合测算</h1>
         <p className="mt-2 text-sm text-muted-foreground">
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