feat: Add Downloaded Scripts tab (#51)

* feat: Add Downloaded Scripts tab

- Create new DownloadedScriptsTab component that shows only downloaded scripts
- Add tab navigation between Available Scripts and Installed Scripts
- Include filtering, searching, and categorization features
- Display statistics for downloaded scripts
- Remove unused script files (2fauth.sh, debian.sh and their install scripts)
- Update main page to include the new tab in navigation

* fix: Resolve ESLint errors in DownloadedScriptsTab

- Fix unescaped apostrophe in empty state message
- Fix empty arrow function by adding proper comment structure

Author: michelroegl-brunner