feat: add pnpm build step to Dockerfile

Add Node.js and pnpm to build stage to run `pnpm build:all` before Jekyll build. This ensures all assets are properly built before site generation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Dockerfile

@@ -2,18 +2,28 @@
 FROM ruby:3.4.1-alpine AS builder
 
 # Install build dependencies
-RUN apk add --no-cache build-base
+RUN apk add --no-cache build-base nodejs npm
+
+# Enable corepack for pnpm
+RUN corepack enable
 
 # Set working directory
 WORKDIR /app
 
-# Copy Gemfile and install dependencies
+# Copy package files and install Node dependencies
+COPY package.json pnpm-lock.yaml ./
+RUN pnpm install --frozen-lockfile
+
+# Copy Gemfile and install Ruby dependencies
 COPY Gemfile Gemfile.lock ./
 RUN bundle install
 
 # Copy source files
 COPY . .
 
+# Build assets with pnpm
+RUN pnpm build:all
+
 # Build Jekyll site
 RUN bundle exec jekyll build