add earnings-date guard — warn when a report falls in the target horizon

Finnhub's earnings calendar now supplies next_earnings_date through the
fundamentals chain; persisted on fundamental_data (migration 006) and exposed in
the fundamentals API. The recommendation panel warns when earnings fall within
the ~30-day target horizon (a report can gap price through stop/target) and
otherwise shows the next date. Informational only.

Deploy: run alembic upgrade (new fundamental_data.next_earnings_date column).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/services/fundamental_service.py

@@ -38,6 +38,7 @@ async def store_fundamental(
     revenue_growth: float | None = None,
     earnings_surprise: float | None = None,
     market_cap: float | None = None,
+    next_earnings_date=None,
     unavailable_fields: dict[str, str] | None = None,
 ) -> FundamentalData:
     """Store or update fundamental data for a ticker.
@@ -61,6 +62,7 @@ async def store_fundamental(
         existing.revenue_growth = revenue_growth
         existing.earnings_surprise = earnings_surprise
         existing.market_cap = market_cap
+        existing.next_earnings_date = next_earnings_date
         existing.fetched_at = now
         existing.unavailable_fields_json = unavailable_fields_json
         record = existing
@@ -71,6 +73,7 @@ async def store_fundamental(
             revenue_growth=revenue_growth,
             earnings_surprise=earnings_surprise,
             market_cap=market_cap,
+            next_earnings_date=next_earnings_date,
             fetched_at=now,
             unavailable_fields_json=unavailable_fields_json,
         )