refactor: Refactor registration forms to use UI components

internal/gateway/handlers/register/ui/name_input.templ

@@ -0,0 +1,8 @@
+package ui
+
+templ NameInput(name string) {
+	<div class="grid grid-cols-1 lg:grid-cols-2 gap-4">
+		<sl-input name="first_name" placeholder="Satoshi" type="text" label="First Name" required autofocus></sl-input>
+		<sl-input name="last_name" placeholder="N" maxlength="1" type="text" label="Last Initial"></sl-input>
+	</div>
+}