Add Kraken hourly OHLC poller with database storage

Fetches Bitcoin hourly candles from the Kraken public REST API
and upserts them into a kraken_hour table on a 5-minute poll interval,
following the existing Integrant component pattern.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

resources/migrations/20260218000000-create-kraken-hour.down.sql

@@ -0,0 +1 @@
+DROP TABLE kraken_hour;