ux: improve about page navigation with breadcrumb and back button

Add breadcrumb navigation and back-to-home button to make About page
navigation clear and user-friendly. Also add related-pages section at
bottom linking to Home, Services, and Blog.

Addresses: users getting lost on About page with no clear way back.

TaxBaik.Web/Pages/About.cshtml

@@ -3,7 +3,22 @@
     ViewData["Title"] = "소개 | 백원숙 세무회계";
 }
 
+<!-- Breadcrumb Navigation -->
+<nav aria-label="breadcrumb" class="py-3" style="background: #F9F7F3; border-bottom: 1px solid #D9D3C4;">
+    <div class="container">
+        <ol class="breadcrumb mb-0">
+            <li class="breadcrumb-item"><a href="/taxbaik/" class="text-decoration-none">홈</a></li>
+            <li class="breadcrumb-item active">소개</li>
+        </ol>
+    </div>
+</nav>
+
 <div class="container py-5">
+    <!-- 돌아가기 버튼 -->
+    <div class="mb-4">
+        <a href="/taxbaik/" class="btn btn-sm btn-outline-secondary">← 홈으로 돌아가기</a>
+    </div>
+
     <!-- Hero Section -->
     <section class="mb-5 pb-5 border-bottom">
         <h1 class="fw-bold mb-4" style="font-size: 2.5rem;">안녕하세요, 백원숙 세무사입니다.</h1>
@@ -122,7 +137,7 @@
     </section>
 
     <!-- CTA Section -->
-    <section class="text-center">
+    <section class="text-center mb-5 pb-5 border-bottom">
         <h3 class="fw-bold mb-3">세금 고민, 이제 끝내세요</h3>
         <p class="text-muted mb-5">무료 상담으로 현재 상황을 진단하고 맞춤형 절세 전략을 받아보세요.</p>
         <div class="d-flex gap-3 justify-content-center flex-wrap">
@@ -130,4 +145,29 @@
             <a href="http://pf.kakao.com/_xoxchTX" target="_blank" class="btn btn-warning btn-lg">카카오로 문의</a>
         </div>
     </section>
+
+    <!-- 관련 페이지 네비게이션 -->
+    <section class="text-center py-5">
+        <h4 class="fw-bold mb-4">다른 페이지 보기</h4>
+        <div class="row g-3 justify-content-center">
+            <div class="col-md-4">
+                <a href="/taxbaik/" class="btn btn-outline-primary btn-sm w-100 py-3">
+                    🏠 홈으로<br/>
+                    <small class="text-muted">서비스 및 최신 정보</small>
+                </a>
+            </div>
+            <div class="col-md-4">
+                <a href="/taxbaik/services" class="btn btn-outline-primary btn-sm w-100 py-3">
+                    📊 전문 서비스<br/>
+                    <small class="text-muted">사업자·부동산·자산 관리</small>
+                </a>
+            </div>
+            <div class="col-md-4">
+                <a href="/taxbaik/blog" class="btn btn-outline-primary btn-sm w-100 py-3">
+                    📝 세무 정보 블로그<br/>
+                    <small class="text-muted">절세팁 및 신고 가이드</small>
+                </a>
+            </div>
+        </div>
+    </section>
 </div>