ux: improve reconnection modal message and styling

- Simplified message: '연결 재설정 중...' with clearer context
- Added polished CSS styling with animation
- Better visual hierarchy and user guidance
- Improves experience when Blazor circuit disconnects during deployment

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

TaxBaik.Web/wwwroot/css/admin.css

@@ -1445,3 +1445,57 @@ textarea:focus-visible {
 @keyframes spin {
   to { transform: rotate(360deg); }
 }
+
+/* Reconnection Modal */
+.admin-reconnect-modal {
+  display: none;
+  position: fixed;
+  top: 0;
+  left: 0;
+  width: 100%;
+  height: 100%;
+  background: rgba(0, 0, 0, 0.5);
+  z-index: 9998;
+  align-items: center;
+  justify-content: center;
+}
+
+.admin-reconnect-modal.components-reconnect-modal {
+  display: flex;
+}
+
+.admin-reconnect-card {
+  background: white;
+  padding: 2rem;
+  border-radius: 8px;
+  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
+  text-align: center;
+  max-width: 400px;
+  display: flex;
+  flex-direction: column;
+  gap: 1rem;
+  animation: slideIn 0.3s ease-out;
+}
+
+.admin-reconnect-card strong {
+  font-size: 1.25rem;
+  color: var(--text-primary);
+  display: block;
+}
+
+.admin-reconnect-card span {
+  color: var(--text-secondary);
+  font-size: 0.95rem;
+  line-height: 1.4;
+}
+
+@keyframes slideIn {
+  from {
+    opacity: 0;
+    transform: translateY(-20px);
+  }
+  to {
+    opacity: 1;
+    transform: translateY(0);
+  }
+}