Move HTML rendering to btcprice, send raw JSON over both WebSockets

Price and Strike WebSockets now emit JSON instead of HTML fragments.
Added Strike WebSocket endpoint and wired strike/ticker into API routes.

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

resources/system.edn

@@ -47,7 +47,8 @@
  {:base-path    "/api"
   :query-fn     #ig/ref :db.sql/query-fn
   :binance      #ig/ref :ws/binance
-  :frankfurter  #ig/ref :frankfurter/rates}
+  :frankfurter  #ig/ref :frankfurter/rates
+  :strike       #ig/ref :strike/ticker}
 
  :ws/binance
  {:query-fn #ig/ref :db.sql/query-fn