東北キャラクター追加とデフォルト変更 (#13)

feat: Enhance audio generation progress visibility

refactor: Update timeout values and remove session recovery steps

feat: Update browser state restoration for Japanese UI

feat: Add Japanese UI text mapping for document and podcast modes

feat: Add browser state persistence for settings changes

fix: Resolve E2E test failures by updating textarea selectors

Revert "feat: Add browser state persistence for podcast script and terms agreement"

feat: Add browser state persistence for podcast script and terms agreement

feat: Implement browser state restoration using localStorage