Added new upload functionality to the editor supporting doc/docx/ppt/pptx/pdf/zip/txt/json files. Includes:
- New upload button with file input
- File type detection utilities (isTextFile, isConvertibleFile)
- Initial markdown sync with trailing whitespace normalization
- Warning messages for unsupported file types
- Add privacy mode to hide IP and user preferences from AI requests
- Add model thinking levels (low/medium/high) for context analysis depth
- Add PWA support with service worker, manifest, and app icons
- Add SettingsPanel for user preferences (theme, background, language)
- Add i18n translations for en/zh/ja/ko/de/fr
- Add Pinia store for centralized settings management
- Update backend to support user preferences and thinking levels
- Update config to use absolute API URLs
ydy0615