Show human-readable timestamps in Kraken minute poller logs

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

src/clj/pmagnus/btcdata/kraken/ohlc_minute.clj

@@ -5,7 +5,9 @@
    [integrant.core :as ig])
   (:import
    [java.net URI]
-   [java.net.http HttpClient HttpRequest HttpResponse$BodyHandlers]))
+   [java.net.http HttpClient HttpRequest HttpResponse$BodyHandlers]
+   [java.time Instant ZoneOffset]
+   [java.time.format DateTimeFormatter]))
 
 (def ^:private kraken-ohlc-url
   "https://api.kraken.com/0/public/OHLC?pair=XBTUSD&interval=1")
@@ -67,7 +69,10 @@
       (save-candles! query-fn candles)
       (when last-ts
         (reset! since-atom last-ts))
-      (log/info "Fetched" (count candles) "Kraken minute candles"))
+      (let [fmt    (DateTimeFormatter/ofPattern "HH:mm")
+            latest (:ts (last candles))
+            ts-str (.format (.atOffset (Instant/ofEpochSecond latest) ZoneOffset/UTC) fmt)]
+        (log/info "Kraken minute:" (count candles) "candles, latest" ts-str "UTC")))
     (count candles)))
 
 (defn- start-poll-loop!