fix(ci): pass Backblaze B2 credentials to process_unarchived_pkgs

The function defaults to Hetzner S3 with HETZNER_S3_*_K3S env vars that
are not set in these workflows, so paws failed with "No compatible
credentials provided". Pass the B2 endpoint/region/bucket and
B2_S3_* secrets explicitly, matching the other S3 calls. Also use
set_codename(NULL) for the build-all-versions codename so it matches
the S3 repo path.

.crow/build-all-versions.yaml

@@ -138,7 +138,7 @@ steps:
         done
       # archive missed packages; first arg is the codename (e.g. "alpine324"),
       # derived via bincraft like the upload step, not paste(OS, OS_VERSION).
-      - /opt/R/$R_VERSION/bin/R -q -e "bincraft::process_unarchived_pkgs(bincraft::set_codename(NULL), Sys.getenv('ARCH'), workers = $NCPUS)"
+      - /opt/R/$R_VERSION/bin/R -q -e "bincraft::process_unarchived_pkgs(bincraft::set_codename(NULL), Sys.getenv('ARCH'), s3_endpoint = 'https://s3.eu-central-003.backblazeb2.com', s3_region = 'eu-central-003', s3_bucket = 'devxy-rpkgs-binaries', s3_access_key_id = Sys.getenv('B2_S3_ACCESS_KEY'), s3_secret_access_key = Sys.getenv('B2_S3_SECRET_KEY'), workers = $NCPUS)"
     backend_options:
       docker:
         resources: