feat(chats-mobile): add resume conversation modal and GitHub button

- Add elegant modal for resume conversation functionality
- Modal shows claude --resume command with copy functionality
- Center Resume button in chat view header
- Add centered GitHub star button in main chat header
- Improve responsive design with three-column header layout
- Enhanced user experience with visual feedback on copy actions

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: davila7