fix(manual-ledger): harden schema init race and sanitize error responses

Co-authored-by: genichin <4282227+genichin@users.noreply.github.com>

tests/test_v1_portfolios_manual_ledger.py

@@ -386,6 +386,31 @@ def test_insufficient_cash_rejected_as_409() -> None:
 
     assert resp.status_code == 409
     assert resp.json()["detail"]["code"] == "INSUFFICIENT_CASH"
+    assert resp.json()["detail"]["message"] == "Insufficient cash balance"
+
+
+def test_manual_ledger_conflict_message_is_sanitized() -> None:
+    repo = _FakeRepo(_portfolio())
+    client = _make_client(repo)
+
+    secret = "SENTINEL_SECRET_TOKEN_12345"
+
+    def _raise_secret(*args: Any, **kwargs: Any) -> LedgerEntry:
+        raise ValueError(f"synthetic backend failure: {secret}")
+
+    repo.record_manual_ledger = _raise_secret  # type: ignore[method-assign]
+
+    resp = client.post(
+        f"/v1/portfolios/{_PORTFOLIO_ID}/ledger/manual",
+        json={"action": "DIVIDEND", "amount": 1, "executed_at": "2026-09-01"},
+        headers=_auth(),
+    )
+
+    assert resp.status_code == 422
+    detail = resp.json()["detail"]
+    assert detail["code"] == "MANUAL_LEDGER_CONFLICT"
+    assert detail["message"] == "Manual ledger request could not be processed"
+    assert secret not in resp.text
 
 
 def test_manual_history_returns_total_value_after() -> None: