Initial commit: Daily tech newsletter worker

A Node.js/TypeScript worker that sends daily AI-generated summaries
of tech news from X/Twitter via Nitter RSS feeds.

Features:
- Fetches tweets from 40+ curated tech accounts via Nitter RSS
- Filters and categorizes by topic (AI/ML, SWE, General Tech)
- Generates AI summaries using OpenRouter (Claude/GPT-4)
- Sends professional HTML email via Brevo SMTP
- Runs on cron schedule inside Docker container
- Instance rotation for Nitter reliability
- Graceful degradation if AI fails

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker/Dockerfile

@@ -0,0 +1,42 @@
+# =============================================================================
+# Build Stage
+# =============================================================================
+FROM node:20-alpine AS builder
+
+WORKDIR /app
+
+# Install dependencies first (better layer caching)
+COPY package*.json ./
+RUN npm ci
+
+# Copy source and build
+COPY tsconfig.json ./
+COPY src ./src
+RUN npm run build
+
+# Prune dev dependencies
+RUN npm prune --production
+
+# =============================================================================
+# Production Stage
+# =============================================================================
+FROM node:20-alpine AS production
+
+# Security: run as non-root user
+RUN addgroup -g 1001 -S nodejs && \
+    adduser -S newsletter -u 1001
+
+WORKDIR /app
+
+# Copy built application
+COPY --from=builder --chown=newsletter:nodejs /app/node_modules ./node_modules
+COPY --from=builder --chown=newsletter:nodejs /app/dist ./dist
+COPY --from=builder --chown=newsletter:nodejs /app/package.json ./
+
+USER newsletter
+
+# Set timezone (can be overridden via env)
+ENV TZ=Europe/Warsaw
+
+# Default command
+CMD ["node", "dist/index.js"]

docker/docker-compose.yml

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+version: '3.8'
+
+services:
+  newsletter-worker:
+    build:
+      context: ..
+      dockerfile: docker/Dockerfile
+    container_name: x-newsletter
+    restart: unless-stopped
+    env_file:
+      - ../.env
+    environment:
+      - NODE_ENV=production
+      - TZ=${CRON_TIMEZONE:-Europe/Warsaw}
+    volumes:
+      # Optional: persist logs
+      - ../logs:/app/logs
+    logging:
+      driver: "json-file"
+      options:
+        max-size: "10m"
+        max-file: "3"
+    # Resource limits
+    deploy:
+      resources:
+        limits:
+          cpus: '0.5'
+          memory: 512M
+        reservations:
+          cpus: '0.25'
+          memory: 256M