Razor Pages 경로 최적화: 절대 경로 → 상대 경로

## 변경사항
- Login.cshtml.cs: /taxbaik/* 절대 경로 제거
  - RedirectUrl: '/taxbaik/admin/dashboard' → '/admin/dashboard'
  - NormalizeRedirectUrl: 경로 정규화 로직 간소화
- 모든 Razor Pages (.cshtml):
  - href='/taxbaik/*' → href='/*' 변경
  - src='/taxbaik/*' → src='/*' 변경
  - Response.Redirect('/taxbaik/*') → Response.Redirect('/*') 변경
- Feed.cshtml: RSS 피드의 절대 URL 유지 (SEO용)

## 원칙
✅ 내부 링크: 상대 경로 사용
✅ 외부 URL (RSS, CanonicalUrl): 절대 URL 유지
✅ Nginx: /taxbaik 프리픽스 자동 처리

## 결과
✅ 빌드: 0 오류, 2 경고
✅ 전체 경로 최적화 완료

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

src/TaxBaik.Web/Pages/Shared/_Footer.cshtml

@@ -26,8 +26,8 @@
         <hr class="my-3" />
         <div class="text-center small text-muted">
             <p>© 2026 백원숙 세무회계. All rights reserved.</p>
-            <a href="/taxbaik/privacy" class="text-decoration-none text-muted me-2">개인정보처리방침</a>
-            <a href="/taxbaik/terms" class="text-decoration-none text-muted">이용약관</a>
+            <a href="/privacy" class="text-decoration-none text-muted me-2">개인정보처리방침</a>
+            <a href="/terms" class="text-decoration-none text-muted">이용약관</a>
         </div>
     </div>
 </footer>

src/TaxBaik.Web/Pages/Shared/_Header.cshtml

@@ -1,6 +1,6 @@
 <header class="sticky-top bg-white border-bottom site-header">
     <nav class="navbar navbar-expand-lg navbar-light container-fluid px-3 py-2">
-        <a class="navbar-brand fw-bold" href="/taxbaik">
+        <a class="navbar-brand fw-bold" href="/">
             <span class="text-primary">백원숙</span> 세무회계
         </a>
         <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
@@ -9,19 +9,19 @@
         <div class="collapse navbar-collapse mt-3 mt-lg-0" id="navbarNav">
             <ul class="navbar-nav ms-auto gap-2 align-items-lg-center">
                 <li class="nav-item">
-                    <a class="nav-link" href="/taxbaik">홈</a>
+                    <a class="nav-link" href="/">홈</a>
                 </li>
                 <li class="nav-item">
-                    <a class="nav-link" href="/taxbaik/about">소개</a>
+                    <a class="nav-link" href="/about">소개</a>
                 </li>
                 <li class="nav-item">
-                    <a class="nav-link" href="/taxbaik/services">서비스</a>
+                    <a class="nav-link" href="/services">서비스</a>
                 </li>
                 <li class="nav-item">
-                    <a class="nav-link" href="/taxbaik/blog">블로그</a>
+                    <a class="nav-link" href="/blog">블로그</a>
                 </li>
                 <li class="nav-item">
-                    <a class="btn btn-primary btn-sm ms-lg-2 w-100 w-lg-auto" href="/taxbaik/contact">상담신청</a>
+                    <a class="btn btn-primary btn-sm ms-lg-2 w-100 w-lg-auto" href="/contact">상담신청</a>
                 </li>
             </ul>
         </div>