feat: 질문지 제출 기능 + 관리자 응답 관리 + iframe 미리보기 수정

- 질문지 HTML에 제출/임시저장 JavaScript 추가 (localStorage 임시저장, API 제출)
- questionnaire_responses 테이블 마이그레이션 (005)
- /api/questionnaire/submit POST 엔드포인트
- 관리자 질문지 응답 목록/상세/상태변경 페이지 및 API
- 관리자 문서 미리보기를 fetch+srcdoc 방식으로 변경 (X-Frame-Options 우회)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/api/admin/questionnaire/[id]/route.ts

@@ -0,0 +1,69 @@
+import { NextResponse } from 'next/server';
+import { createAdminClient } from '@/lib/supabase/admin';
+import { verifyAdminTokenNode } from '@/lib/admin-auth';
+import { cookies } from 'next/headers';
+
+export const runtime = 'nodejs';
+
+async function checkAuth() {
+  const cookieStore = await cookies();
+  const token = cookieStore.get('admin_token')?.value;
+  return token && verifyAdminTokenNode(token);
+}
+
+// 질문지 응답 상세 조회
+export async function GET(
+  request: Request,
+  { params }: { params: Promise<{ id: string }> }
+) {
+  if (!(await checkAuth())) {
+    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
+  }
+
+  const { id } = await params;
+  const admin = createAdminClient();
+  const { data, error } = await admin
+    .from('questionnaire_responses')
+    .select('*')
+    .eq('id', id)
+    .single();
+
+  if (error) {
+    console.error('[Admin Questionnaire] DB error:', error);
+    return NextResponse.json({ error: '조회 실패' }, { status: 500 });
+  }
+
+  return NextResponse.json({ data });
+}
+
+// 상태/메모 업데이트
+export async function PATCH(
+  request: Request,
+  { params }: { params: Promise<{ id: string }> }
+) {
+  if (!(await checkAuth())) {
+    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
+  }
+
+  const { id } = await params;
+  const body = await request.json();
+  const { status, admin_notes } = body;
+
+  const updates: Record<string, unknown> = {};
+  if (status) updates.status = status;
+  if (admin_notes !== undefined) updates.admin_notes = admin_notes;
+  if (status === 'reviewed') updates.reviewed_at = new Date().toISOString();
+
+  const admin = createAdminClient();
+  const { error } = await admin
+    .from('questionnaire_responses')
+    .update(updates)
+    .eq('id', id);
+
+  if (error) {
+    console.error('[Admin Questionnaire] Update error:', error);
+    return NextResponse.json({ error: '업데이트 실패' }, { status: 500 });
+  }
+
+  return NextResponse.json({ success: true });
+}

app/api/admin/questionnaire/route.ts

@@ -0,0 +1,32 @@
+import { NextResponse } from 'next/server';
+import { createAdminClient } from '@/lib/supabase/admin';
+import { verifyAdminTokenNode } from '@/lib/admin-auth';
+import { cookies } from 'next/headers';
+
+export const runtime = 'nodejs';
+
+async function checkAuth() {
+  const cookieStore = await cookies();
+  const token = cookieStore.get('admin_token')?.value;
+  return token && verifyAdminTokenNode(token);
+}
+
+// 질문지 응답 목록 조회
+export async function GET() {
+  if (!(await checkAuth())) {
+    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
+  }
+
+  const admin = createAdminClient();
+  const { data, error } = await admin
+    .from('questionnaire_responses')
+    .select('*')
+    .order('created_at', { ascending: false });
+
+  if (error) {
+    console.error('[Admin Questionnaire] DB error:', error);
+    return NextResponse.json({ error: '데이터 조회 실패' }, { status: 500 });
+  }
+
+  return NextResponse.json({ data });
+}