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--everything is withdrawn.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 Withdrawn flags are listed in one place and proven to exit 2.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/test_e2e_cli_contract_only_sql.py

@@ -0,0 +1,33 @@
+import unittest
+
+from .helpers import run
+
+WITHDRAWN_FLAGS = ["--dump-only", "--dump-only-sql", "--everything"]
+
+
+class TestE2ECLIContractOnlySql(unittest.TestCase):
+    def test_help_mentions_the_flag(self) -> None:
+        cp = run(["baudolo", "--help"], capture=True, check=True)
+        out = (cp.stdout or "") + "\n" + (cp.stderr or "")
+        self.assertIn(
+            "--only-sql",
+            out,
+            f"Expected '--only-sql' to appear in --help output. Output:\n{out}",
+        )
+
+    def test_a_withdrawn_flag_is_rejected(self) -> None:
+        for flag in WITHDRAWN_FLAGS:
+            with self.subTest(flag=flag):
+                cp = run(["baudolo", flag], capture=True, check=False)
+                self.assertEqual(
+                    cp.returncode,
+                    2,
+                    f"Expected exitcode 2 for unknown args, got {cp.returncode}\n"
+                    f"STDOUT={cp.stdout}\nSTDERR={cp.stderr}",
+                )
+                err = (cp.stderr or "") + "\n" + (cp.stdout or "")
+                # Argparse typically prints "unrecognized arguments"
+                self.assertTrue(
+                    ("unrecognized arguments" in err) or ("usage:" in err.lower()),
+                    f"Expected argparse-style error output. Output:\n{err}",
+                )