build: switch to native Hugo TailwindCSS pipeline, align Dockerfile with pivoine.art

Replaces the PostCSS + autoprefixer toolchain with Hugo's native
css.TailwindCSS pipe (via @tailwindcss/cli), matching the setup already
in use on pivoine.art. Dockerfile now builds on hugomods/hugo with a
matched Hugo/Node version instead of manually installing Hugo onto
node:22-alpine.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S3xLyuoN6uzfCYBo8kVoSn

Dockerfile

@@ -1,25 +1,20 @@
 # ── Stage 1: builder ────────────────────────────────────────────────────────
-FROM node:22-alpine AS builder
-
-# Install Hugo extended + build tools
-RUN apk add --no-cache \
-    curl \
-    git \
-    libc6-compat \
-    && HUGO_VERSION=0.147.2 \
-    && curl -sSL "https://github.com/gohugoio/hugo/releases/download/v${HUGO_VERSION}/hugo_extended_${HUGO_VERSION}_linux-amd64.tar.gz" \
-    | tar -xz -C /usr/local/bin hugo
+# hugomods image bundles Hugo Extended + Node at matching, tested versions —
+# Hugo's css.TailwindCSS execs node_modules/.bin/tailwindcss during the build,
+# and pnpm-workspace.yaml's preferSymlinkedExecutables makes that a plain
+# symlink Hugo's exec-security check accepts (see layouts/partials/head.html).
+FROM hugomods/hugo:debian-node-0.165.0 AS builder
 
 # Install pnpm
-RUN corepack enable && corepack prepare pnpm@latest --activate
+RUN npm install -g pnpm
 
 WORKDIR /app
 
-# Install dependencies
-COPY package.json pnpm-lock.yaml* ./
+# Copy package files first (for layer caching)
+COPY package.json pnpm-lock.yaml pnpm-workspace.yaml ./
 RUN pnpm install --frozen-lockfile
 
-# Copy source
+# Copy source files
 COPY . .
 
 # Build site

hugo.toml

@@ -36,6 +36,9 @@ noClasses = true
 [build]
 writeStats = true
 
+[security.exec]
+allow = ['^(dart-)?sass$', '^go$', '^git$', '^node$', '^npx$', '^tailwindcss$']
+
 [[menus.footer]]
 name = "Imprint"
 url = "/imprint/"

layouts/partials/head.html

@@ -90,8 +90,8 @@
   />
 </noscript>
 
-<!-- CSS via Hugo Pipes + PostCSS + Tailwind v4 -->
-{{- $css := resources.Get "css/main.css" | css.PostCSS -}}
+<!-- CSS via Hugo Pipes + Tailwind v4 (native css.TailwindCSS, no PostCSS) -->
+{{- $css := resources.Get "css/main.css" | css.TailwindCSS -}}
 {{- if eq hugo.Environment "production" -}}
   {{- $css = $css | minify | fingerprint "sha256" -}}
 {{- end -}}

package.json

@@ -11,10 +11,7 @@
     "format:check": "prettier --check \"layouts/**/*.html\" \"assets/**/*.css\" \"assets/**/*.js\" \"content/**/*.md\" \"*.toml\""
   },
   "devDependencies": {
-    "@tailwindcss/postcss": "^4.0.0",
-    "autoprefixer": "^10.4.0",
-    "postcss": "^8.5.0",
-    "postcss-cli": "^11.0.0",
+    "@tailwindcss/cli": "^4.0.0",
     "prettier": "^3.8.3",
     "prettier-plugin-go-template": "^0.0.15",
     "prettier-plugin-toml": "^2.0.6",

pnpm-workspace.yaml

@@ -0,0 +1,3 @@
+preferSymlinkedExecutables: true
+allowBuilds:
+  '@parcel/watcher': true

postcss.config.js

@@ -1,6 +0,0 @@
-module.exports = {
-  plugins: {
-    "@tailwindcss/postcss": {},
-    autoprefixer: {},
-  },
-};