Rewrite btcprice from Clojure to Python FastAPI

Replace the Clojure Kit application with a Python FastAPI app that
produces identical HTML output. WebSocket proxy, Danish number
formatting, and HTMX integration all preserved.

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

.gitignore

@@ -1,15 +1,6 @@
-/target
-/classes
-/checkouts
-profiles.clj
-pom.xml
-pom.xml.asc
-*.jar
-*.class
-/.lein-*
-/.nrepl-port
-/.cpcache
-/.clj-kondo
+__pycache__/
+*.pyc
+.venv/
 /node_modules
 /log
 .DS_Store