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-lock.json

@@ -16,6 +16,7 @@
         "@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",
@@ -23,6 +24,7 @@
         "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",
@@ -1603,6 +1605,13 @@
         "@types/node": "*"
       }
     },
+    "node_modules/@types/js-yaml": {
+      "version": "4.0.9",
+      "resolved": "https://registry.npmjs.org/@types/js-yaml/-/js-yaml-4.0.9.tgz",
+      "integrity": "sha512-k4MGaQl5TGo/iipqb2UDG2UwjXziSWkh0uysQelTlJpX1qGlpUZYm8PnO4DxG1qBomtJUdYJ6qR6xdIah10JLg==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/@types/json-schema": {
       "version": "7.0.15",
       "resolved": "https://registry.npmjs.org/@types/json-schema/-/json-schema-7.0.15.tgz",
@@ -1982,7 +1991,6 @@
       "version": "2.0.1",
       "resolved": "https://registry.npmjs.org/argparse/-/argparse-2.0.1.tgz",
       "integrity": "sha512-8+9WqebbFzpX9OR+Wa6O29asIogeRMzcGtAINdpMHHyAg10f05aSFVBbcEqGf/PXw1EjAZ+q2/bEBg3DvurK3Q==",
-      "dev": true,
       "license": "Python-2.0"
     },
     "node_modules/array-buffer-byte-length": {
@@ -4340,7 +4348,6 @@
       "version": "4.1.1",
       "resolved": "https://registry.npmjs.org/js-yaml/-/js-yaml-4.1.1.tgz",
       "integrity": "sha512-qQKT4zQxXl8lLwBtHMWwaTcGfFOZviOJet3Oy/xmGk2gZH677CJM9EvtfdSkgWcATZhj/55JZ0rmy3myCT5lsA==",
-      "dev": true,
       "license": "MIT",
       "dependencies": {
         "argparse": "^2.0.1"