Update VOICEVOX character list and docs (#19)

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

feat: Update browser state restoration for Japanese UI

fix: Resolve E2E test failures by updating textarea selectors

refactor: Optimize timeout values for improved test performance

style: Apply comprehensive ruff formatting across entire codebase

feat: Migrate from isort, black, flake8 to ruff for unified linting and formatting

feat: Enhance audio generation progress display with comprehensive tracking

Add audio recovery feature and enhance audio state management

refactor: Update file upload and URL extraction tabs for improved clarity and functionality

Fix mypy typing errors

Refactor unit tests for SessionManager and TextProcessor classes