fix(backup): match the engine on the image name

has_image tested the pattern against the raw .Config.Image, so anything in the reference could decide which dump tool runs -- including the registry host and the tag. A swarm node that hosts the local registry prefixes every pull with its own name, and that node is named after the app under test, so a Postgres container reads as svc-db-mariadb-swarm-mgr-01:5000/postgres_custom:17-3.5. dumps.py tries mariadb before postgres, matched on the hostname, and dumped Postgres with mariadb-dump: exit 127, the image does not ship it. The BackupException took the backup unit down with it.

image_name strips digest, tag and registry host and matches on the repository path, so the decision rests on the image alone. Same intent as the exact --images-* matching from f9776ac, applied to the one place that commit did not reach. Tags stop deciding too: xwiki_custom:lts-postgres-tomcat no longer reads as Postgres.

The e2e reproduces the shape without a registry -- a docker tag is enough for .Config.Image to carry the reference verbatim -- and asserts a real pg_dump lands. Under the old code mariadb-dump aborts and no dump file exists.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/baudolo/backup/docker.py

@@ -9,9 +9,29 @@ def get_image_info(container: str) -> str:
     )[0]
 
 
+def image_name(container: str) -> str:
+    """The image's repository path, without registry host, tag or digest.
+
+    A swarm node that hosts the local registry puts its own hostname in front
+    of every pull, so the raw reference of a Postgres container can read
+    `svc-db-mariadb-swarm-mgr-01:5000/postgres_custom:17-3.5`. Matching the
+    whole reference finds "mariadb" there and dumps the database with
+    mariadb-dump, which the Postgres image does not ship (exit 127). Tags bite
+    the same way: `xwiki_custom:lts-postgres-tomcat`.
+    """
+    reference = get_image_info(container).strip().split("@", 1)[0]
+    head, _, tail = reference.rpartition("/")
+    tail = tail.split(":", 1)[0]
+    if head:
+        registry = head.split("/", 1)[0]
+        if "." in registry or ":" in registry or registry == "localhost":
+            head = head.partition("/")[2]
+    return f"{head}/{tail}" if head else tail
+
+
 def has_image(container: str, pattern: str) -> bool:
-    """Return True if container's image contains the pattern."""
-    return pattern in get_image_info(container)
+    """Return True if the container's image name contains the pattern."""
+    return pattern in image_name(container)
 
 
 def docker_volume_names() -> list[str]: