formats all dart files using `dart format .` from the root project dir
this makes the code style repeatable by new contributors and makes PR review easier
- Added flutter_linkify package to auto-detect and linkify URLs in chat messages.
- Implemented LinkHandler class to manage link tap confirmations and URL launching.
- Updated chat_screen.dart to use Linkify for displaying message text with links.
- Registered url_launcher plugin for handling URL launches across platforms.
- Updated pubspec.yaml and pubspec.lock to include new dependencies.
- Cleaned up untranslated.json by removing unused translations.
