My .NET Docker image was 900MB - here's how I fixed it (and what I got wrong with JWT)

I'm a CS student working on a side project - a .NET 8 REST API for a healthcare management system we're building at university. Nothing fancy, just something to practice real-world backend stuff. Last week I had two moments where I genuinely felt dumb. Sharing them here so maybe someone else doesn't waste the same 3 hours I did. The Docker problem: why is my image 900MB?? I followed a basic tutorial to containerize my API. Dockerfile looked like this: FROM mcr.microsoft.com/dotnet/sdk:8.0 WORKDI