feat: Initial purchase order views, login seems to be broken though.

Sources/App/Views/Main.swift

@@ -28,7 +28,7 @@ struct MainPage<Inner: HTML>: SendableHTMLDocument where Inner: Sendable {
   }
 
   var body: some HTML {
-    header {
+    header(.class("header")) {
       Logo()
       if displayNav {
         Navbar()