Add EUR/DKK rate display support and run-docker Makefile target

Safelist Tailwind classes for currency rate HTML fragments from btcdata
WebSocket. Add make run-docker target that connects to Docker btcdata
on port 4101.

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

Makefile

@@ -1,7 +1,7 @@
 include .env
 export
 
-.PHONY: clean run repl tailwind test uberjar
+.PHONY: clean run run-docker repl tailwind test uberjar
 
 clean:
 	rm -rf target
@@ -9,6 +9,9 @@ clean:
 run:
 	clj -M:dev -e "(dev-prep!) (go)" -r
 
+run-docker:
+	BTCDATA_URL=http://localhost:4101 clj -M:dev -e "(dev-prep!) (go)" -r
+
 repl:
 	clj -M:dev:nrepl