Tutorial: Setting up ASE with GPAW for band structure calculations

I wrote a practical walkthrough for students who want to run GPAW from Python without juggling too many environment variables. The tutorial covers reproducible conda setup, PAW dataset checks, k-point path generation, and plotting with matplotlib. The main pain point was making sure MPI launch commands behave consistently across local and cluster environments.

I included a minimal silicon example and a section on common numerical pitfalls, especially basis-set convergence. Happy to extend this with spin-polarized examples if that helps newcomers.