ADR 003: Next.js

This ADR is inherited from personal-site. Read the canonical source ADR.

Source summary: With React selected as the UI library (see ADR 002), I need a meta-framework to handle routing, building, and rendering. While I could use vanilla React (SPA) or a bundler like Vite directly, a meta-framework provides better performance (SSG/SSR), SEO, and developer experience.