Add S3-backed storage to prevent data loss

- New lib/storage.mjs: async S3 backup on every queue/log save
- Versioned S3 bucket (claw-apply-data) keeps every revision
- Auto-restore from S3 if local file is missing or corrupt
- saveQueue/saveLog now validate data type before writing
  (prevents the exact bug that corrupted the queue)
- IAM role attached to EC2 instance for credential-free S3 access
- Config: storage.type = "local" (default) or "s3"

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

config/settings.example.json

@@ -25,5 +25,11 @@
   "browser": {
     "provider": "kernel",
     "playwright_path": null
+  },
+  "storage": {
+    "type": "local",
+    "_note": "Set type to 's3' for S3-backed storage. Requires @aws-sdk/client-s3 and IAM permissions.",
+    "bucket": "claw-apply-data",
+    "region": "us-west-2"
   }
 }