Prepare governed S1 offsite upload

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a02994-7685-7940-bf34-3555b8256018

spec/s1-backup.yaml

@@ -10,6 +10,10 @@ retention:
   max_total_bytes: 268435456
   freshness_hours: 26
 
+offsite:
+  required_before_prune: true
+  receipt_root: /opt/backup/railiance/infra/offsite-receipts
+
 artifacts:
   os-config:
     format: tar.gz

spec/s1-offsite-owner-acceptance.yaml

@@ -0,0 +1,6 @@
+schema_version: "1.0"
+contract_sha256: pending
+status: pending
+owner_repo: railiance-platform
+decision_id: null
+accepted_at: null

spec/s1-offsite.yaml

@@ -0,0 +1,30 @@
+schema_version: "1.0"
+
+route_id: railiance-backup-offsite-lane
+owner_repo: railiance-platform
+owner_acceptance_file: spec/s1-offsite-owner-acceptance.yaml
+
+provider:
+  kind: nextcloud-file-drop
+  base_url: https://nx4069.your-storageshare.de/public.php/dav/filesdrop
+  remote_prefix: railiance-infra
+
+transport:
+  method: PUT
+  content_type: application/x-tar
+  if_none_match: "*"
+  success_codes: [201, 204]
+  authentication: basic-token-empty-password
+  secret_env: RAILIANCE_BACKUP_NC_TOKEN
+  response_body: suppressed
+
+envelope:
+  format: deterministic-ustar
+  members:
+    - manifest.json
+    - receipt.json
+    - os-config.tar.gz.age
+    - packages.txt.age
+  object_name_template: "railiance-infra__{bundle_id}__s1-envelope.tar"
+
+receipt_root: /opt/backup/railiance/infra/offsite-receipts