Split data layer into btcdata service

Remove DB, Binance WebSocket, and Kraken pollers from btcprice.
UI now uses vanilla EventSource connecting to btcdata for live
price updates. btcprice is now a pure UI service with no database.

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

resources/system.edn

@@ -32,34 +32,9 @@
  {:routes #ig/ref :router/routes
   :env    #ig/ref :system/env}
 
- :db.sql/connection
- {:jdbc-url #env JDBC_URL}
-
- :db.sql/query-fn
- {:conn        #ig/ref :db.sql/connection
-  :options     {}
-  :filename    "queries.sql"}
-
- :db.sql/migrations
- {:store            :database
-  :db               {:datasource #ig/ref :db.sql/connection}
-  :migrate-on-init? true}
-
  :reitit.routes/api
- {:base-path "/api"
-  :query-fn  #ig/ref :db.sql/query-fn}
+ {:base-path "/api"}
 
  :reitit.routes/ui
- {:base-path ""
-  :query-fn  #ig/ref :db.sql/query-fn
-  :binance   #ig/ref :ws/binance}
-
- :ws/binance
- {:query-fn #ig/ref :db.sql/query-fn
-  :uri      "wss://stream.binance.com:9443/ws/btcusdt@trade"}
-
- :kraken/ohlc
- {:query-fn #ig/ref :db.sql/query-fn}
-
- :kraken/ohlc-day
- {:query-fn #ig/ref :db.sql/query-fn}}
+ {:base-path   ""
+  :btcdata-url #or [#env BTCDATA_URL "http://localhost:4100"]}}