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>

resources/css/input.css

@@ -1,2 +1,2 @@
 @import "tailwindcss";
-@source "../../src/**/*.clj";
+@source "../../app/**/*.py";

resources/public/favicon.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><text y=".9em" font-size="90">₿</text></svg>

resources/system.edn

@@ -1,43 +0,0 @@
-{:system/env #profile {:dev :dev :test :test :prod :prod}
-
- :server/http
- {:port    #long #or [#env PORT 4000]
-  :host    #or [#env HTTP_HOST "0.0.0.0"]
-  :handler #ig/ref :handler/ring}
-
- :handler/ring
- {:router    #ig/ref :router/core
-  :api-path  "/api"
-  :site-defaults-config
-  {:params    {:keywordize true
-               :multipart  true
-               :nested     true}
-   :cookies   true
-   :session   {:flash        true
-               :cookie-attrs {:http-only true
-                              :same-site :strict}}
-   :security  {:anti-forgery   false
-               :xss-protection {:enable? true :mode :block}
-               :frame-options  :sameorigin}
-   :static    {:resources "public"}
-   :responses {:not-modified-responses true
-               :absolute-redirects     true
-               :content-types          true
-               :default-charset        "utf-8"}}}
-
- :router/routes
- {:routes #ig/refset :reitit/routes}
-
- :router/core
- {:routes #ig/ref :router/routes
-  :env    #ig/ref :system/env}
-
- :reitit.routes/api
- {:base-path "/api"}
-
- :reitit.routes/ui
- {:base-path ""}
-
- :reitit.routes/ws-proxy
- {:base-path   ""
-  :btcdata-url #or [#env BTCDATA_URL "http://localhost:4100"]}}