Add Kraken daily OHLC poller with database storage

Polls Kraken API for 1-day BTC/USD candles aligned to 00:01 UTC,
mirroring the existing hourly poller pattern.

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

resources/queries.sql

@@ -25,3 +25,20 @@ SET open = EXCLUDED.open,
 -- :doc Get the most recent Kraken hourly candle by timestamp
 SELECT ts, open, high, low, close, vwap, volume, trade_count, created_at
 FROM kraken_hour ORDER BY ts DESC LIMIT 1
+
+-- :name upsert-kraken-day! :! :n
+-- :doc Upsert a Kraken daily OHLC candle
+INSERT INTO kraken_day (ts, open, high, low, close, vwap, volume, trade_count)
+VALUES (:ts, :open, :high, :low, :close, :vwap, :volume, :trade-count)
+ON CONFLICT (ts) DO UPDATE
+SET open = EXCLUDED.open,
+    high = EXCLUDED.high,
+    low  = EXCLUDED.low,
+    close = EXCLUDED.close,
+    vwap  = EXCLUDED.vwap,
+    volume = EXCLUDED.volume,
+    trade_count = EXCLUDED.trade_count
+
+-- :name get-latest-kraken-day :? :1
+-- :doc Get the most recent Kraken daily candle by timestamp
+SELECT ts FROM kraken_day ORDER BY ts DESC LIMIT 1