Show sats instead of BTC on donation page, refactor CSS

* Show sats instead of BTC on donation page
* Use number delimiters on both donation page and wallet page
* Refactor donation page CSS into Tailwind directives

app/javascript/stylesheets/application.scss

@@ -1,4 +1,4 @@
-// version 3
+// version 4
 @import "tailwindcss/base";
 @import "tailwindcss/components";
 @import "tailwindcss/utilities";