feat(mailu): add ops.py + backup/restore tests + update PARITY.md (P4 now covered via PR#3)

tests/mailu/test_restore.py

@@ -0,0 +1,26 @@
+"""mailu — RESTORE overlay: assert the seeded mailbox is back after restore.
+
+ops.pre_restore deleted citest@<domain> from the admin sqlite to simulate data loss; this
+overlay verifies that abra app restore brings the user back (the /data sqlite volume is
+restored from the backup taken by pre_backup, which contained the seeded user)."""
+
+from __future__ import annotations
+
+import os
+import sys
+
+sys.path.insert(0, os.path.dirname(__file__))
+import _mailu  # noqa: E402
+
+_CI_LOCALPART = "citest"
+
+
+def test_restore_returns_mailbox(live_app):
+    email = f"{_CI_LOCALPART}@{live_app}"
+    cfg = _mailu.config_export(live_app)
+    emails = _mailu.user_emails(cfg)
+    assert email in emails, (
+        f"seeded mailbox {email!r} not found in config-export after restore; "
+        f"restore did not return the pre-mutation mail data. "
+        f"users present: {emails}"
+    )