Scaffold dd0c/alert: ingestion, correlation engine, HMAC validation, tests

- Webhook ingestion: HMAC validation for Datadog/PagerDuty/OpsGenie with 5-min timestamp freshness
- Payload normalizers: canonical alert schema with severity mapping per provider
- Correlation engine: time-window grouping, late-alert attachment (2x window), FakeClock for testing
- InMemoryWindowStore for unit tests
- Tests: 12 HMAC validation cases, 5 normalizer cases, 7 correlation engine cases
- PostgreSQL schema with RLS: tenants, incidents, alerts, webhook_secrets, notification_configs
- Free tier enforcement columns (alert_count_month, reset_at)
- Fly.io config, Dockerfile, Gitea Actions CI

products/03-alert-intelligence/Dockerfile

@@ -0,0 +1,14 @@
+FROM node:22-slim AS builder
+WORKDIR /app
+COPY package.json package-lock.json* ./
+RUN npm ci
+COPY . .
+RUN npm run build
+
+FROM node:22-slim
+WORKDIR /app
+COPY --from=builder /app/dist ./dist
+COPY --from=builder /app/node_modules ./node_modules
+COPY --from=builder /app/package.json ./
+EXPOSE 3000
+CMD ["node", "dist/index.js"]