fix(docker): use node:20-slim base image instead of unavailable Playwright image

The Playwright Docker image v1.58.2-noble doesn't exist on MCR, breaking
the CI build. Switch to node:20-slim and install Playwright chromium at
build time for resilience against future version mismatches.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -1,17 +1,22 @@
-FROM mcr.microsoft.com/playwright/javascript:v1.58.2-noble
+FROM node:20-slim
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    curl \
+    && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app
 
 COPY package.json package-lock.json* ./
 RUN npm ci --production 2>/dev/null || npm install --production
 
+# Install Playwright browsers + OS dependencies (chromium only to save space)
+RUN npx playwright install --with-deps chromium
+
 COPY src/ ./src/
 
-# Create cache directory owned by pwuser (default user in playwright image)
-RUN mkdir -p /app/cache && chown -R pwuser:pwuser /app/cache
+# Create cache directory
+RUN mkdir -p /app/cache
 
 EXPOSE 3001 3002
 
-USER pwuser
-
 CMD ["node", "src/index.js"]