fix: CSS layers were silently dropped by postcss-import

postcss-import requires ALL @import statements before any rules.
The :root {} override block between Open Props import and layer
imports caused all 11 layer files to be silently dropped — only
Open Props variables made it through (29KB of definitions, zero
actual styles).

Fix: move :root overrides after all imports. Add explicit PostCSS
build step to deploy.sh (Hugo Pipes runs from a temp dir that
breaks relative paths anyway).

Result: 102KB compiled CSS = Open Props + all ASW layers.

deploy.sh

@@ -4,5 +4,6 @@ set -euo pipefail
 cd ~/projects/asw
 git pull origin main --ff-only
 npm ci --prefer-offline 2>/dev/null
+npx postcss assets/css/asw.css -o assets/css/asw-built.css
 hugo
 echo "[$(date -u +%Y-%m-%dT%H:%M:%SZ)] Deploy complete" >> /tmp/asw-deploy.log