feat: Replace status screens with liquid versions

- maintenance.njk is now a single status.liquid
- All status screens use liquid
- Simplify structure

source/screens/demo/pages/maintenance.liquid

@@ -0,0 +1,13 @@
+---
+title: Maintenance
+---
+{% assign pageBase = "../../" -%}
+{% assign pageClass = "h_full_view" %}
+{%- layout "hippie/status.liquid" %}
+
+{% block body %}
+<hgroup id="root" class="txt_center">
+	<h1 class="txt_hero txt_gradient">HIPPIE</h1>
+	<p>Diese Seite wird gerade gewartet.</p>
+</hgroup>
+{% endblock %}