feat: 에러 처리 개선 + 커스텀 확인 모달 + 관리자 테스트

- 에러 코드 기반 한국어 매핑 (8개 코드, parseError 개선)
- window.confirm → 커스텀 ConfirmDialog (다크 테마, Promise 기반)
- launch URL 파라미터 ticket → token 통일
- 관리자 테스트 27개 추가 (공지사항 12 + 다운로드 6 + 유저 9)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/confirm/ConfirmProvider.jsx

@@ -0,0 +1,46 @@
+import { useState, useCallback, useMemo, useRef } from 'react';
+import { ConfirmContext } from './confirmContextValue';
+import './Confirm.css';
+
+export function ConfirmProvider({ children }) {
+  const [dialog, setDialog] = useState(null);
+  const resolveRef = useRef(null);
+
+  const confirm = useCallback((message) => {
+    return new Promise((resolve) => {
+      resolveRef.current = resolve;
+      setDialog({ message });
+    });
+  }, []);
+
+  const handleConfirm = useCallback(() => {
+    resolveRef.current?.(true);
+    resolveRef.current = null;
+    setDialog(null);
+  }, []);
+
+  const handleCancel = useCallback(() => {
+    resolveRef.current?.(false);
+    resolveRef.current = null;
+    setDialog(null);
+  }, []);
+
+  const value = useMemo(() => confirm, [confirm]);
+
+  return (
+    <ConfirmContext.Provider value={value}>
+      {children}
+      {dialog && (
+        <div className="confirm-overlay" onClick={handleCancel}>
+          <div className="confirm-dialog" role="alertdialog" aria-modal="true" aria-label={dialog.message} onClick={(e) => e.stopPropagation()}>
+            <p className="confirm-message">{dialog.message}</p>
+            <div className="confirm-actions">
+              <button className="confirm-btn confirm-btn-cancel" onClick={handleCancel}>취소</button>
+              <button className="confirm-btn confirm-btn-ok" onClick={handleConfirm} autoFocus>확인</button>
+            </div>
+          </div>
+        </div>
+      )}
+    </ConfirmContext.Provider>
+  );
+}