fix(backup): detect the engine by its dump tool, not by the image name

36b2336 matched postgres and mariadb against the image's repository path. That name is not a property of the software: a dedicated Postgres inside an app's own stack is tagged <app>-database or postgis/postgis and carries no engine token at all, so it was never recognised, never dumped, and its data directory was copied as files without a single warning - the fallback notice hangs on found_db, which stayed false.

The container is now asked what it can run. pg_dumpall, mariadb-dump and mysqldump are probed by executing them, not by asking a shell for them, because a distroless image has no shell and would deny every tool it ships. The verdict is cached per image ID rather than per container, so replicas of one image cost a single probe.

Because the probe names the tool it found, the dump uses it instead of the hardcoded /usr/bin/mariadb-dump, which makes an image that ships only mysqldump dumpable rather than silently file-copied.

image_name and has_image are gone with their registry-host and tag stripping; the trap they worked around cannot occur when nothing reads the name. get_image_info stays, since the --images-* lists match exact references.

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

src/baudolo/backup/db.py

@@ -69,12 +69,17 @@ def backup_database(
     container: str,
     volume_dir: str,
     db_type: str,
+    dump_tool: str,
     databases_df: pandas.DataFrame,
     database_containers: list[str],
 ) -> bool:
     """
     Backup databases for a given DB container.
 
+    Args:
+        dump_tool: the MariaDB client found in the container, so an image
+            that ships only mysqldump is dumped with the tool it has.
+
     Returns True if at least one dump was produced.
     """
     instance_name = get_instance(container, database_containers)
@@ -114,7 +119,7 @@ def backup_database(
         if db_type == "mariadb":
             # Force TCP so auth matches '<user>'@'%' instead of socket -> 'localhost'.
             cmd = (
-                f"docker exec {container} /usr/bin/mariadb-dump "
+                f"docker exec {container} {dump_tool} "
                 f"-h 127.0.0.1 --protocol=tcp "
                 f"-u {user} -p{password} {db_name}"
             )