Comprehensive Project Management System

I'm looking for a solution that combines efficient task tracking and email integration. The platform should be flexible, available as a website, mobile app, and a desktop application, hence developers who can pull this off across multiple platforms are highly desired. Here are the essential features:

Task Management:
- Option to check off tasks as they get completed.
- Display deadlines for each task.
- Provide the time spent on each task.
- Utilize AI during the process to text task to assignees, record the activity, move the deadline, write a status to client on a PDF form, email it to said client, and send an email with a preset subject and each items completed (as a separate email for each task)

Email Integration:
- Notifications for task completion and approaching deadlines.
- Email time spent on task
- Email with preset subject information and information in the body of the email

Ideal freelancers should have:
- Relevant experience in building project management tools.
- Proven skills in cross-platform development.
- Understanding of robust email systems.
- The ability to create intuitive and user-friendly interfaces.
- Use of AI in these processes

Please include any previous similar projects in your proposal, and don't hesitate to ask any questions you might have.