fix(holdings): /holdings/cost-basis WAC row에 fee_amount 편입 (QC보정)

get_holdings_cost_basis 핸들러의 row dict에 fee_amount 누락으로
/holdings/cost-basis의 cost_basis_per_unit이 매수 수수료 미편입값을
반환하던 버그 수정. /pnl/realized 핸들러와 동일하게 e.fee_amount 포함.
테스트: buy fee>0 케이스(1000.5 단언) + fee=0 회귀 케이스 추가.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VHtM5Ws1HKCKQ4JGi6GRb5

tests/test_v1_portfolios_holdings.py

@@ -78,6 +78,7 @@ def _make_entry(
     quantity: float,
     price: float,
     executed_at: datetime,
+    fee_amount: float = 0.0,
 ) -> LedgerEntry:
     return LedgerEntry(
         ledger_entry_id=ledger_entry_id,
@@ -87,7 +88,7 @@ def _make_entry(
         side=side,
         quantity=quantity,
         price=price,
-        fee_amount=0.0,
+        fee_amount=fee_amount,
         tax_amount=0.0,
         executed_at=executed_at,
         recorded_at=executed_at,
@@ -535,3 +536,68 @@ def test_portfolio_id_in_response_matches_request() -> None:
         resp = client.get(_PATH, headers={"Authorization": "Bearer tok"})
     assert resp.status_code == 200
     assert resp.json()["portfolio_id"] == _PORTFOLIO_ID
+
+
+# ---------------------------------------------------------------------------
+# QC보정: buy fee>0 케이스 — cost_basis_per_unit이 fee 편입값인지 확인
+# buy 10@1000 fee=5 → cost_basis_per_unit = (10*1000 + 5) / 10 = 1000.5
+# ---------------------------------------------------------------------------
+
+def test_cost_basis_per_unit_includes_buy_fee() -> None:
+    """buy fee>0 케이스: cost_basis_per_unit이 매수 fee 편입값을 반환한다.
+
+    buy 10주 @ 1,000원, fee=5원 → WAC = (10*1000 + 5) / 10 = 1000.5
+    REQ-043 Notes: 매수 fee를 cost basis에 포함.
+    """
+    settings = _make_settings()
+    trades = [
+        _make_entry(
+            ledger_entry_id=1,
+            side="buy",
+            quantity=10,
+            price=1_000,
+            fee_amount=5.0,
+            executed_at=datetime(2026, 6, 1, 9, 0, tzinfo=timezone.utc),
+        ),
+    ]
+    repo = _make_service_repo(
+        portfolio=_make_portfolio(asset_quantity=10.0),
+        trades=trades,
+    )
+    with _with_repo(repo):
+        client = _make_client(settings)
+        resp = client.get(_PATH, headers={"Authorization": "Bearer tok"})
+    assert resp.status_code == 200
+    body = resp.json()
+    # (10 * 1000 + 5) / 10 = 1000.5
+    assert body["cost_basis_per_unit"] == pytest.approx(1000.5)
+    assert body["total_cost_basis"] == pytest.approx(10_005.0)
+
+
+def test_cost_basis_per_unit_zero_fee_unchanged() -> None:
+    """buy fee=0 케이스: fee 편입 추가 후에도 fee=0이면 기존 값 그대로.
+
+    buy 10주 @ 1,000원, fee=0 → WAC = 1000.0 (회귀 확인)
+    """
+    settings = _make_settings()
+    trades = [
+        _make_entry(
+            ledger_entry_id=1,
+            side="buy",
+            quantity=10,
+            price=1_000,
+            fee_amount=0.0,
+            executed_at=datetime(2026, 6, 1, 9, 0, tzinfo=timezone.utc),
+        ),
+    ]
+    repo = _make_service_repo(
+        portfolio=_make_portfolio(asset_quantity=10.0),
+        trades=trades,
+    )
+    with _with_repo(repo):
+        client = _make_client(settings)
+        resp = client.get(_PATH, headers={"Authorization": "Bearer tok"})
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["cost_basis_per_unit"] == pytest.approx(1000.0)
+    assert body["total_cost_basis"] == pytest.approx(10_000.0)