feat: 토정비결 및 PDF 저장 기능 추가

- 토정비결 페이지 구현 (연간/월별 운세)
- 분야별 운세 (재물, 건강, 관운, 애정)
- PDF 저장 기능 구현 (jsPDF + html2canvas)
- 모든 결과 페이지에 PDF 다운로드 기능 추가
- PDFButton 재사용 가능한 컴포넌트 생성
- 홈페이지에 토정비결 링크 추가
- 페이지 간 네비게이션 링크 업데이트

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

app/fortune/page.tsx

@@ -1,5 +1,6 @@
 import Link from 'next/link';
 import { calculateSaju } from '@/lib/saju-calculator';
+import PDFButton from '../components/PDFButton';
 
 interface PageProps {
   searchParams: Promise<{
@@ -118,7 +119,7 @@ export default async function FortunePage({ searchParams }: PageProps) {
       </nav>
 
       {/* Content */}
-      <div className="max-w-6xl mx-auto px-4 py-12">
+      <div id="pdf-content" className="max-w-6xl mx-auto px-4 py-12">
         {/* Header */}
         <div className="text-center mb-12">
           <h1 className="text-4xl md:text-5xl font-bold text-gray-900 mb-4">
@@ -218,7 +219,7 @@ export default async function FortunePage({ searchParams }: PageProps) {
         </div>
 
         {/* 다른 메뉴 */}
-        <div className="grid md:grid-cols-3 gap-6">
+        <div className="grid md:grid-cols-2 lg:grid-cols-4 gap-6">
           <Link
             href={`/result?${new URLSearchParams(params as any).toString()}`}
             className="bg-white rounded-xl p-6 shadow-lg hover:shadow-xl transition text-center group"
@@ -229,7 +230,7 @@ export default async function FortunePage({ searchParams }: PageProps) {
           </Link>
 
           <Link
-            href="/"
+            href="/compatibility"
             className="bg-white rounded-xl p-6 shadow-lg hover:shadow-xl transition text-center group"
           >
             <div className="text-4xl mb-3">💕</div>
@@ -238,13 +239,19 @@ export default async function FortunePage({ searchParams }: PageProps) {
           </Link>
 
           <Link
-            href="/"
+            href="/tojeong"
             className="bg-white rounded-xl p-6 shadow-lg hover:shadow-xl transition text-center group"
           >
             <div className="text-4xl mb-3">🎋</div>
             <h3 className="text-xl font-bold text-gray-900 mb-2">토정비결</h3>
             <p className="text-gray-600 text-sm">한 해의 운세 보기</p>
           </Link>
+
+          <PDFButton
+            elementId="pdf-content"
+            filename={`오늘의운세_${todayYear}${todayMonth}${todayDay}.pdf`}
+            buttonText="운세 PDF 저장"
+          />
         </div>
       </div>