fix: switch market data sources from prev_bars to intraday_bars

The market_api sources were configured with endpoint='prev_bars' which
only fetches a single previous-day bar per ticker. Changed to
'intraday_bars' which fetches hourly bars for today from Polygon's
/v2/aggs/ticker/{ticker}/range/1/hour/{today}/{today} endpoint.

Updated: seed script, beta DB (50 sources), production DB (50 sources).
This gives ~7-8 hourly price bars per trading day per ticker instead
of 1 daily bar.

services/symbol_registry/seed.py

@@ -191,7 +191,7 @@ SOURCES_PER_COMPANY = [
         "credibility_score": 0.9,
         "config": {
             "provider": "polygon",
-            "endpoint": "prev_bars",
+            "endpoint": "intraday_bars",
             "adjusted": True,
         },
     },