feat(offsite-backup): olsitec-foundation bucket + scoped creds on home MinIO

CONTRACT_004 offsite target (ADR-004 'second self-hosted location'). @pulumi/minio
program (modeled on olsicloud4 modules/minio): bucket 'olsitec-foundation' +
scoped IAM user/policy + service account on minio.wob.olsitec.de:19000.

Verified: scoped SA can put/list/delete in its bucket, DENIED cross-bucket. Admin
creds + scoped creds via ENV/state only (gitignored), never committed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

package.json

@@ -6,7 +6,8 @@
     "workspaces": [
         "packages/*",
         "bootstrap",
-        "provision"
+        "provision",
+        "offsite-backup"
     ],
     "devDependencies": {
         "typescript": "^5.0.0"