feat: add ledger backup safety workflow

confirm dcy-002 and add REQ/BAT evidence

add ledger backup/status metadata workflow

document restore as runbook/script-only guarded operation

add synthetic DB backup/restore smoke tests

tests/test_backup_workflow.py

@@ -0,0 +1,80 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+from jarca_ledger_mcp import service
+
+
+def test_db_status_reports_metadata_without_sensitive_rows(tmp_path):
+    db_path = str(tmp_path / "ledger.sqlite3")
+    service.create_ledger_transaction(
+        "2026-06-01",
+        "expense",
+        12_000,
+        category="식비",
+        subcategory="카페",
+        merchant="SENTINEL_MERCHANT",
+        counterparty="SENTINEL_COUNTERPARTY",
+        raw_payload="SENTINEL_RAW_PAYLOAD",
+        db_path=db_path,
+    )
+
+    status = service.get_ledger_db_status(db_path=db_path)
+
+    assert status["success"] is True
+    assert status["db_path"] == str(Path(db_path).resolve())
+    assert status["exists"] is True
+    assert status["sha256"]
+    assert status["integrity_check"] == "ok"
+    assert status["table_counts"]["transactions"] == 1
+    dumped = repr(status)
+    assert "SENTINEL_MERCHANT" not in dumped
+    assert "SENTINEL_COUNTERPARTY" not in dumped
+    assert "SENTINEL_RAW_PAYLOAD" not in dumped
+
+
+def test_create_list_and_status_ledger_backup_with_retention(tmp_path):
+    db_path = str(tmp_path / "ledger.sqlite3")
+    backup_dir = str(tmp_path / "backups")
+    service.create_ledger_account("테스트 계좌", db_path=db_path)
+    before = service.get_ledger_db_status(db_path=db_path)
+
+    created = service.create_ledger_backup(db_path=db_path, backup_dir=backup_dir, retention_days=30, retention_count=20)
+
+    assert created["success"] is True
+    assert created["source_db"]["sha256"] == before["sha256"]
+    assert created["backup"]["path"].startswith(str(Path(backup_dir).resolve()))
+    assert Path(created["backup"]["path"]).exists()
+    assert created["backup"]["sha256"]
+    assert created["backup"]["integrity_check"] == "ok"
+    assert created["backup"]["table_counts"] == created["source_db"]["table_counts"]
+    assert created["restore_policy"]["mcp_restore_exposed"] is False
+
+    listed = service.list_ledger_backups(backup_dir=backup_dir, include_hash=True)
+    assert listed["success"] is True
+    assert listed["count"] == 1
+    assert listed["backups"][0]["sha256"] == created["backup"]["sha256"]
+
+    backup_status = service.get_ledger_backup_status(created["backup"]["path"])
+    assert backup_status["success"] is True
+    assert backup_status["backup"]["integrity_check"] == "ok"
+    assert backup_status["backup"]["table_counts"]["accounts"] == 1
+
+
+def test_backup_retention_keeps_recent_count_and_prunes_older_extras(tmp_path):
+    db_path = str(tmp_path / "ledger.sqlite3")
+    backup_dir = tmp_path / "backups"
+    service.create_ledger_transaction("2026-06-01", "income", 1000, category="수입", db_path=db_path)
+
+    for i in range(3):
+        old = backup_dir / f"ledger_20200101000{i}000000.sqlite3"
+        old.parent.mkdir(parents=True, exist_ok=True)
+        old.write_text("old", encoding="utf-8")
+
+    created = service.create_ledger_backup(db_path=db_path, backup_dir=str(backup_dir), retention_days=0, retention_count=2)
+
+    assert created["success"] is True
+    remaining = sorted(p.name for p in backup_dir.glob("*.sqlite3"))
+    assert len(remaining) == 2
+    assert Path(created["backup"]["path"]).name in remaining
+    assert len(created["retention"]["pruned_paths"]) == 2