Three bugs found during task 20 verify, all fixed:
1. Tailwind CLI does NOT read postcss.config.js. Switched Dockerfile to
npx postcss + postcss-cli so the postcss plugin chain actually runs.
2. postcss-import was not installed but app.css uses @import for the
primitive component files. Added postcss-import + cssnano (for prod
minification under --env production).
3. @import statements must come BEFORE any other rules per CSS spec.
app.css had @tailwind base/components ABOVE @import, so postcss-import
silently skipped every component @import. Moved all @imports to the
top, @tailwind directives below. Bundle went from 121KB with 0 wd-*
classes to 138KB with 116 wd-* classes.
Also added tailwind safelist for wd-/is-/nav-dev-badge so the wave-2
migration of HTML files cannot accidentally tree-shake primitives.
