Scaffold dd0c/cost: Welford baseline, anomaly scorer, governance engine, tests

- Welford online algorithm for running mean/stddev baselines
- Anomaly scorer: z-score → 0-100 mapping, property-based tests (10K runs, fast-check)
- Governance engine: 14-day auto-promotion with FP rate gate, injectable Clock
- Panic mode: defaults to active (safe) when Redis unreachable
- Tests: 12 scorer cases (incl 2x 10K property-based), 9 governance cases, 3 panic mode cases
- PostgreSQL schema with RLS: baselines (optimistic locking), anomalies, remediation_actions
- Fly.io config, Dockerfile

products/05-aws-cost-anomaly/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"]