feat: add SVG favicon matching header logo

Create a static SVG favicon replicating the nav logo — a forward slash
on a dark (#09090b) square with the brand light (#fafafa) text colour.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

templates/base.html

@@ -6,6 +6,7 @@
     <meta name="viewport" content="width=device-width, initial-scale=1" />
     <title>{% block title %}No Hype AI{% endblock %}</title>
     {% block head_meta %}{% endblock %}
+    <link rel="icon" href="{% static 'favicon.svg' %}" type="image/svg+xml" />
     <link rel="preconnect" href="https://fonts.googleapis.com">
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
     <link href="https://fonts.googleapis.com/css2?family=Fira+Code:wght@400;500&family=Inter:wght@400;500;600&family=Space+Grotesk:wght@500;700;900&display=swap" rel="stylesheet">