Add S3/MinIO storage for deployment previews

- Add S3 client helper (src/lib/s3.ts) with upload/download functions
- Add /api/deployments/[uuid]/preview endpoint for presigned URLs
- Update DeploymentDashboard to fetch and display preview images
- Install @aws-sdk/client-s3 and @aws-sdk/s3-request-presigner

Storage: MinIO bucket nuc-portal-previews with dedicated service account

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package.json

@@ -10,6 +10,8 @@
     "lint": "eslint"
   },
   "dependencies": {
+    "@aws-sdk/client-s3": "^3.984.0",
+    "@aws-sdk/s3-request-presigner": "^3.984.0",
     "@tanstack/react-table": "^8.21.3",
     "next": "16.1.6",
     "pg": "^8.18.0",