fix(backup,ci): make databases.csv optional and upgrade Docker CLI in image

- Handle missing or empty databases.csv gracefully with warnings and empty DataFrame
- Add unit tests for robust databases.csv loading behavior
- Adjust seed tests to assert warnings across multiple print calls
- Replace Debian docker.io with docker-ce-cli to avoid Docker API version mismatch
- Install required build tools (curl, gnupg) for Docker repo setup

https://chatgpt.com/share/697e6d9d-6458-800f-9d12-1e337509be4e

tests/unit/backup/test_app_databases_csv.py

@@ -0,0 +1,77 @@
+import io
+import os
+import tempfile
+import unittest
+from contextlib import redirect_stderr
+
+import pandas as pd
+
+# Adjust if your package name/import path differs.
+from baudolo.backup.app import _load_databases_df
+
+
+EXPECTED_COLUMNS = ["instance", "database", "username", "password"]
+
+
+class TestLoadDatabasesDf(unittest.TestCase):
+    def test_missing_csv_is_handled_with_warning_and_empty_df(self) -> None:
+        with tempfile.TemporaryDirectory() as td:
+            missing_path = os.path.join(td, "does-not-exist.csv")
+
+            buf = io.StringIO()
+            with redirect_stderr(buf):
+                df = _load_databases_df(missing_path)
+
+            stderr = buf.getvalue()
+            self.assertIn("WARNING:", stderr)
+            self.assertIn("databases.csv not found", stderr)
+
+            self.assertIsInstance(df, pd.DataFrame)
+            self.assertListEqual(list(df.columns), EXPECTED_COLUMNS)
+            self.assertTrue(df.empty)
+
+    def test_empty_csv_is_handled_with_warning_and_empty_df(self) -> None:
+        with tempfile.TemporaryDirectory() as td:
+            empty_path = os.path.join(td, "databases.csv")
+            # Create an empty file (0 bytes)
+            with open(empty_path, "w", encoding="utf-8") as f:
+                f.write("")
+
+            buf = io.StringIO()
+            with redirect_stderr(buf):
+                df = _load_databases_df(empty_path)
+
+            stderr = buf.getvalue()
+            self.assertIn("WARNING:", stderr)
+            self.assertIn("exists but is empty", stderr)
+
+            self.assertIsInstance(df, pd.DataFrame)
+            self.assertListEqual(list(df.columns), EXPECTED_COLUMNS)
+            self.assertTrue(df.empty)
+
+    def test_valid_csv_loads_without_warning(self) -> None:
+        with tempfile.TemporaryDirectory() as td:
+            csv_path = os.path.join(td, "databases.csv")
+
+            content = "instance;database;username;password\nmyapp;*;dbuser;secret\n"
+            with open(csv_path, "w", encoding="utf-8") as f:
+                f.write(content)
+
+            buf = io.StringIO()
+            with redirect_stderr(buf):
+                df = _load_databases_df(csv_path)
+
+            stderr = buf.getvalue()
+            self.assertEqual(stderr, "")  # no warning expected
+
+            self.assertIsInstance(df, pd.DataFrame)
+            self.assertListEqual(list(df.columns), EXPECTED_COLUMNS)
+            self.assertEqual(len(df), 1)
+            self.assertEqual(df.loc[0, "instance"], "myapp")
+            self.assertEqual(df.loc[0, "database"], "*")
+            self.assertEqual(df.loc[0, "username"], "dbuser")
+            self.assertEqual(df.loc[0, "password"], "secret")
+
+
+if __name__ == "__main__":
+    unittest.main()