Add kraken_minute table with 15-second polling

1-minute OHLC candles from Kraken, polled every 15 seconds to keep the
in-progress candle fresh. Unlike hourly/daily pollers, this one keeps
the last candle and upserts it as it updates.

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

resources/queries.sql

@@ -155,6 +155,23 @@ SELECT id, event_id, occurred_at, exchange, fiat_amount, fiat_currency,
 FROM deposits
 ORDER BY occurred_at DESC, id DESC
 
+-- :name upsert-kraken-minute! :! :n
+-- :doc Upsert a Kraken minute OHLC candle
+INSERT INTO kraken_minute (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-minute :? :1
+-- :doc Get the most recent Kraken minute candle timestamp
+SELECT ts FROM kraken_minute ORDER BY ts DESC LIMIT 1
+
 -- :name get-wallet-balances :? :*
 -- :doc Compute sats balance per wallet from events
 SELECT w.id, w.name,