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.up.sql

@@ -0,0 +1,11 @@
+CREATE TABLE kraken_hour (
+  ts          BIGINT         NOT NULL PRIMARY KEY,
+  open        NUMERIC(18,8)  NOT NULL,
+  high        NUMERIC(18,8)  NOT NULL,
+  low         NUMERIC(18,8)  NOT NULL,
+  close       NUMERIC(18,8)  NOT NULL,
+  vwap        NUMERIC(18,8)  NOT NULL,
+  volume      NUMERIC(24,8)  NOT NULL,
+  trade_count INTEGER        NOT NULL,
+  created_at  TIMESTAMPTZ    NOT NULL DEFAULT NOW()
+);