fix(backup): treat 7z exit code 1 (warning) as success in archive_staging

Exit code 1 from 7z means a non-fatal warning — the archive IS created,
just some files couldn't be compressed (e.g. broken symlinks, special
files). Previously the function required filtered output to be empty
alongside rc=1, causing any non-errno=2 stderr line to abort the entire
backup and discard the archive.

Now any rc=1 is treated as success (warning is still logged).

.gitea/workflows/haven-notify.yaml

@@ -109,4 +109,4 @@ jobs:
         with:
           kube_config: ${{ secrets.KUBE_CONFIG }}
           deployment_name: haven-notify
-          namespace: default
+          namespace: infra

k8s/automated-nfs-backup.sh

@@ -437,7 +437,7 @@ archive_staging() {
     fi
     if (( rc == 0 )); then
         return 0
-    elif (( rc == 1 )) && [[ -z "$filtered_output" ]]; then
+    elif (( rc == 1 )); then
         return 0
     fi
     return 1