fix: preserve schema 15 compatibility for v0.1.8

tests/test_monthly_settlement_approved_cashflow_fingerprint_schema.py

@@ -51,7 +51,7 @@ def test_same_version_existing_db_upgrade_is_idempotent_and_preserves_rows(tmp_p
         assert conn.execute("SELECT name, sql FROM sqlite_master WHERE type IN ('table', 'index') AND name NOT LIKE 'monthly_settlement%' AND name <> 'sqlite_sequence' ORDER BY name").fetchall() == before_tables
 
 
-def test_schema16_db_missing_field_gets_only_targeted_additive_column(tmp_path):
+def test_schema15_db_missing_field_gets_only_targeted_additive_column(tmp_path):
     path = str(tmp_path / "legacy16.sqlite3")
     init_db(path)
     with sqlite3.connect(path) as conn:
@@ -69,7 +69,7 @@ def test_schema16_db_missing_field_gets_only_targeted_additive_column(tmp_path):
         )
         conn.execute("INSERT INTO monthly_settlement SELECT id,month,basis_date,status,version,memo,created_by,created_at,updated_by,updated_at,reviewed_by,reviewed_at,review_fingerprint,approved_by,approved_at,approved_version,approved_fingerprint,approval_reason,approval_flags_json,closed_by,closed_at,cancelled_by,cancelled_at,cancellation_reason FROM monthly_settlement_without_fingerprint")
         conn.execute("DROP TABLE monthly_settlement_without_fingerprint")
-        conn.execute("INSERT INTO schema_meta(key,value) VALUES('schema_version','16') ON CONFLICT(key) DO UPDATE SET value='16'")
+        conn.execute("INSERT INTO schema_meta(key,value) VALUES('schema_version','15') ON CONFLICT(key) DO UPDATE SET value='15'")
         conn.execute(
             "INSERT INTO monthly_settlement(id,month,basis_date,status,version,created_by,created_at,updated_by,updated_at) "
             "VALUES ('m1','2026-10','2026-10-31','draft',1,'u','t','u','t')"