Add real-time BTC price feed via Binance WebSocket

Connect to Binance trade stream, persist prices to binance_price table
(throttled to every 5s), and live-update the home page via HTMX polling.

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

resources/migrations/20260217000000-create-binance-price.down.sql

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

resources/migrations/20260217000000-create-binance-price.up.sql

@@ -0,0 +1,5 @@
+CREATE TABLE binance_price (
+  id          BIGSERIAL PRIMARY KEY,
+  price       NUMERIC(18,8) NOT NULL,
+  recorded_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);

resources/queries.sql

@@ -1,2 +1,9 @@
 -- queries for btcprice
--- Add HugSQL queries here as tables are created
+
+-- :name insert-binance-price! :! :n
+-- :doc Insert a Binance BTC price
+INSERT INTO binance_price (price) VALUES (:price)
+
+-- :name get-latest-binance-price :? :1
+-- :doc Get the most recent Binance BTC price
+SELECT price, recorded_at FROM binance_price ORDER BY id DESC LIMIT 1

resources/system.edn

@@ -51,4 +51,8 @@
 
  :reitit.routes/ui
  {:base-path ""
-  :query-fn  #ig/ref :db.sql/query-fn}}
+  :query-fn  #ig/ref :db.sql/query-fn}
+
+ :ws/binance
+ {:query-fn #ig/ref :db.sql/query-fn
+  :uri      "wss://stream.binance.com:9443/ws/btcusdt@trade"}}