fix(phase1): ad-channels API 입력 견고성 — JSON 파싱 try/catch + 문자열 타입 가드

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/api/admin/ad-channels/route.ts

@@ -31,8 +31,14 @@ export async function POST(request: Request) {
     return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
   }
 
-  const body = await request.json();
-  const name = (body.name as string | undefined)?.trim();
+  let body: Record<string, unknown>;
+  try {
+    body = await request.json();
+  } catch {
+    return NextResponse.json({ error: '잘못된 요청 형식' }, { status: 400 });
+  }
+
+  const name = typeof body.name === 'string' && body.name.trim() ? body.name.trim() : null;
 
   if (!name) {
     return NextResponse.json({ error: '채널명을 입력해주세요.' }, { status: 400 });
@@ -41,7 +47,11 @@ export async function POST(request: Request) {
   const supabase = createAdminClient();
   const { data, error } = await supabase
     .from('ad_channels')
-    .insert({ name, url: body.url?.trim() || null, memo: body.memo?.trim() || null })
+    .insert({
+      name,
+      url: typeof body.url === 'string' && body.url.trim() ? body.url.trim() : null,
+      memo: typeof body.memo === 'string' && body.memo.trim() ? body.memo.trim() : null,
+    })
     .select()
     .single();