AhmedTyson/threedos-backend — reverse-engineered prompt

Build me a clean PHP backend submissions repo for my ThreeDOS backend delegate work. I want it organized by tasks, where each task folder has the assignment brief, diagrams if needed, database setup, and the actual backend solution.

Include one task for an Organizo platform where users can manage items with full create, read, update, and delete actions, filter by priority, and archive old items. Include another task for an Airline Management System with a REST style API, database design notes, and careful transaction handling so related changes either all succeed or all fail.

Use plain PHP with PDO, keep the code easy to read, and add enough comments so I can explain it later. Make the README look polished with a short intro, task index, structure overview, and author section. If anything needs setup, include simple instructions so someone can run each task locally without guessing.