feat(backup)!: mandatory repo-name and databases-csv, --only-files, --only-sql

Two defaults could not be right. --repo-name fell back to the literal 'backup-docker-to-local' while its help promised the git repo folder name, which nothing ever derived. --databases-csv pointed inside the installed package directory, where credentials must not live; when it applied, load_databases_df read a missing file as empty and the run finished without a single dump and without an error. Both are required now, --repo-name in the restore CLI too. The file itself may still be absent - babadcb's tolerance is untouched, only the path must be named.

--everything is withdrawn. Its one effect was to ignore --images-no-stop-required, which is what leaving that list empty already does, and its branch was the default path minus the requires_stop check. No caller, no test, and help and README described it differently.

--dump-only-sql becomes --only-sql, and --only-files joins it as the opposite half: no dumps at all, every volume as files. They form a mutually exclusive group. A host that only copies files has no business holding database passwords, so --databases-csv is not required there and is never read.

The smallest valid argv turned out to be written four times across the test tree; it now lives once. Withdrawn flags are listed in one place and proven to exit 2.

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

tests/e2e/helpers/fixtures.py

@@ -24,7 +24,7 @@ def backup_run(
     database_containers: list[str],
     images_no_stop_required: list[str],
     images_no_backup_required: list[str] | None = None,
-    dump_only_sql: bool = False,
+    only_sql: bool = False,
 ) -> None:
     cmd = [
         "baudolo",
@@ -45,8 +45,8 @@ def backup_run(
     ]
     if images_no_backup_required:
         cmd += ["--images-no-backup-required", *images_no_backup_required]
-    if dump_only_sql:
-        cmd += ["--dump-only-sql"]
+    if only_sql:
+        cmd += ["--only-sql"]
 
     try:
         run(cmd, capture=True, check=True)