feat(CORE-002): add GLD share quote conversion seam

tests/test_data_service_quote_units.py

@@ -0,0 +1,59 @@
+from __future__ import annotations
+
+import pytest
+
+from app.services.cache import CacheService
+from app.services.data_service import DataService
+
+
+class _CacheStub(CacheService):
+    def __init__(self, initial: dict[str, object] | None = None) -> None:
+        self._store = dict(initial or {})
+
+    async def get_json(self, key: str):  # type: ignore[override]
+        return self._store.get(key)
+
+    async def set_json(self, key: str, value):  # type: ignore[override]
+        self._store[key] = value
+        return True
+
+
+@pytest.mark.asyncio
+async def test_get_quote_upgrades_cached_gld_quote_with_missing_quote_unit() -> None:
+    cache = _CacheStub(
+        {
+            "quote:GLD": {
+                "symbol": "GLD",
+                "price": 404.19,
+                "change": 0.0,
+                "change_percent": 0.0,
+                "updated_at": "2026-03-25T00:00:00+00:00",
+                "source": "cache",
+            }
+        }
+    )
+    service = DataService(cache=cache)
+
+    quote = await service.get_quote("GLD")
+
+    assert quote["quote_unit"] == "share"
+    assert cache._store["quote:GLD"]["quote_unit"] == "share"
+
+
+@pytest.mark.asyncio
+async def test_get_quote_preserves_missing_quote_unit_for_unsupported_symbols() -> None:
+    cache = _CacheStub(
+        {
+            "quote:BTC-USD": {
+                "symbol": "BTC-USD",
+                "price": 70000.0,
+                "updated_at": "2026-03-25T00:00:00+00:00",
+                "source": "cache",
+            }
+        }
+    )
+    service = DataService(cache=cache, default_symbol="BTC-USD")
+
+    quote = await service.get_quote("BTC-USD")
+
+    assert "quote_unit" not in quote