feat(cost): add zombie hunter, Slack interactions, composite scoring

- Zombie resource hunter: detects idle EC2/RDS/EBS/EIP/NAT resources
- Slack interactive handler: acknowledge, snooze, create-ticket actions
- Composite anomaly scorer: Z-Score + rate-of-change + pattern + novelty
- Cold-start fast path for new resources (<7 days data)
- 005_zombies.sql migration

products/06-runbook-automation/saas/package.json

@@ -19,6 +19,7 @@
     "@slack/web-api": "^7.1.0",
     "fastify": "^4.28.0",
     "ioredis": "^5.4.0",
+    "js-yaml": "^4.1.1",
     "jsonwebtoken": "^9.0.2",
     "pg": "^8.12.0",
     "pino": "^9.1.0",
@@ -26,6 +27,7 @@
     "zod": "^3.23.0"
   },
   "devDependencies": {
+    "@types/js-yaml": "^4.0.9",
     "@types/jsonwebtoken": "^9.0.6",
     "@types/node": "^20.14.0",
     "@types/pg": "^8.11.0",