Day 3/100: Adding JWT Authentication - Secure APIs with FastAPI

Part of my 100 Days of Code journey. Today we go from single-user to multi-user with proper security. The Challenge Add JWT-based authentication to the Task Management API, enabling user registration, login, and secure task isolation. The Problem: Yesterday's API works great for one person. But what if multiple people use it? How do we know who owns which tasks? How do we keep data private? The Solution: Implement industry-standard JWT authentication with password hashing, user management, and authorization. Why Authentication Matters Let me tell you what happens without authentication: If you build APIs without authentication, you don't really have an application. You have an open database with HTTP access. Imagine a production task manager where: User A could see User B's tasks. User B could delete User A's tasks. That would be chaos. This isn't a feature. It's a security nightmare. Today, we fix all of this. What We're Building Authentication has three parts: Registration - Create a