style: Integrate search form and table into single card container

- Consolidate filter/search form with data table in one card
- Separate with <hr class='my-0'> for visual hierarchy
- Remove redundant card-mb spacing and gaps
- Unified layout for Blog, Clients, Inquiries pages
- Cleaner, more cohesive data display

Applied to:
- Blog/Index.cshtml
- Clients/Index.cshtml
- Inquiries/Index.cshtml

Announcements and Faqs already have integrated structure (no search form)

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

src/TaxBaik.Web/Pages/Admin/Blog/Index.cshtml

@@ -7,33 +7,25 @@
 <section class="admin-page-shell">
     @await Html.PartialAsync("_AdminPageHeader", new TaxBaik.Web.Models.AdminPageHeaderModel("콘텐츠", "블로그 관리", "검색, 발행 상태, 작성일 기준의 블로그 목록입니다.", "/admin/blog/create", "새 글 작성"))
 
-    <form method="get" class="card mb-3">
+    <div class="card">
         <div class="card-body">
-            <div class="row g-3 align-items-end">
-                <div class="col-md-6">
-                    <label class="form-label" for="SearchQuery">검색</label>
-                    <input class="form-control" id="SearchQuery" name="searchQuery" value="@Model.SearchQuery" placeholder="제목 또는 본문 검색" />
+            <form method="get">
+                <div class="row g-3 align-items-end">
+                    <div class="col-md-6">
+                        <label class="form-label" for="SearchQuery">검색</label>
+                        <input class="form-control" id="SearchQuery" name="searchQuery" value="@Model.SearchQuery" placeholder="제목 또는 본문 검색" />
+                    </div>
+                    <div class="col-md-6 d-flex gap-2">
+                        <button class="btn btn-primary" type="submit">검색</button>
+                        <a class="btn btn-outline-secondary" href="/admin/blog">초기화</a>
+                        <a class="btn btn-outline-secondary" href="/admin/blog?showArchived=true">내린 글 보기</a>
+                    </div>
                 </div>
-                <div class="col-md-6 d-flex gap-2">
-                    <button class="btn btn-primary" type="submit">검색</button>
-                    <a class="btn btn-outline-secondary" href="/admin/blog">초기화</a>
-                    <a class="btn btn-outline-secondary" href="/admin/blog?showArchived=true">내린 글 보기</a>
-                </div>
-            </div>
+            </form>
         </div>
-    </form>
-
-    @if (Model.Items.Count == 0)
-    {
-        <div class="card">
-            <div class="card-body py-4">
-                @await Html.PartialAsync("_EmptyState", "블로그 글이 없습니다.")
-            </div>
-        </div>
-    }
-    else
-    {
-        <div class="card">
+        @if (Model.Items.Count > 0)
+        {
+            <hr class="my-0" />
             <div class="table-responsive">
                 <table class="table table-vcenter card-table table-hover">
                     <thead>
@@ -67,8 +59,14 @@
                     </tbody>
                 </table>
             </div>
-        </div>
-    }
+        }
+        else
+        {
+            <div class="card-body py-4">
+                @await Html.PartialAsync("_EmptyState", "블로그 글이 없습니다.")
+            </div>
+        }
+    </div>
 </section>