결재 템플릿 단계 적용 구현

- ApprovalTemplate 엔티티·DTO·원격 리포지토리 추가
- ApprovalController에 템플릿 로딩/적용 상태와 assignSteps 호출 연동
- ApprovalPage 단계 탭에 템플릿 선택 UI 및 적용 확인 다이얼로그 구현
- 템플릿 적용 단위 테스트와 IMPLEMENTATION_TASKS 현황 갱신

lib/widgets/components/superport_dialog.dart

@@ -0,0 +1,40 @@
+import 'package:flutter/material.dart';
+import 'package:shadcn_ui/shadcn_ui.dart';
+
+/// 공통 모달 다이얼로그.
+Future<T?> showSuperportDialog<T>({
+  required BuildContext context,
+  required String title,
+  String? description,
+  required Widget body,
+  List<Widget>? actions,
+  bool barrierDismissible = true,
+}) {
+  return showDialog<T>(
+    context: context,
+    barrierDismissible: barrierDismissible,
+    builder: (dialogContext) {
+      final theme = ShadTheme.of(dialogContext);
+      return Dialog(
+        insetPadding: const EdgeInsets.all(24),
+        clipBehavior: Clip.antiAlias,
+        child: ShadCard(
+          title: Text(title, style: theme.textTheme.h3),
+          description: description == null
+              ? null
+              : Text(description, style: theme.textTheme.muted),
+          footer: Row(
+            mainAxisAlignment: MainAxisAlignment.end,
+            children: actions ?? <Widget>[
+              ShadButton.ghost(
+                onPressed: () => Navigator.of(dialogContext).pop(),
+                child: const Text('닫기'),
+              ),
+            ],
+          ),
+          child: body,
+        ),
+      );
+    },
+  );
+}