feat: implement page vertical layout structure - add flex column to body, set min-height 100vh, complete mainpagework item 1

app/globals.css

@@ -32,7 +32,9 @@
 }
 
 body {
-  height: 100vh;
+  display: flex;
+  flex-direction: column;
+  min-height: 100vh;
   background: var(--background);
   color: var(--foreground);
   font-family: Arial, Helvetica, sans-serif;

app/page.tsx

@@ -2,7 +2,7 @@ import Link from "next/link";
 
 export default function Home() {
   return (
-    <div className="min-h-screen bg-white">
+    <div className="flex flex-col flex-1 bg-white">
       {/* 헤더 */}
       <header className="bg-white shadow-sm sticky top-0 z-50">
         <div className="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8">