Add Strike quote endpoint for real sats price with fee-adjusted amount

Use POST /v1/currency-exchange-quotes to get actual buy price including
spread, matching the Strike app. Fee is cached daily to calculate the
pre-fee amount from the configured total (default 55 EUR). Store
quote_sats in the strike_price DB table.

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

resources/system.edn

@@ -64,5 +64,6 @@
  {:url #or [#env FRANKFURTER_URL "http://localhost:8080"]}
 
  :strike/ticker
- {:query-fn #ig/ref :db.sql/query-fn
-  :api-key  #env STRIKE_API_KEY}}
+ {:query-fn        #ig/ref :db.sql/query-fn
+  :api-key         #env STRIKE_API_KEY
+  :sats-eur-amount #or [#env SATS_EUR_AMOUNT "55"]}}