High-Quality Software Projects for GitHub Portfolio -- 2

I'm seeking three complete software projects with clean code and full documentation, suitable for study and GitHub portfolio enhancement.

Requirements:
- Tech Stack: Java/Spring Boot
- Application Type: Web Application
- Features: User Authentication, Payment Integration, Interactive Dashboards

Each project must include:
1) Clean and modular code
2) Detailed README.md with:
- Project description
- Setup instructions
- Tech stack used
- Screenshots (if applicable)
3) Proper documentation:
- Architecture/design overview
- Database schema (if any)
- API documentation (if backend project)
4) Bonus: Git-style commit history

Please provide:
- Ideas for 3 project topics
- Timeline for delivery
- Total cost for all three projects

Looking forward to your proposals!