Add image upload preview functionality; update titles and templates for consistency

Co-authored-by: Copilot <copilot@github.com>

frontend/app/templates/admin.html

@@ -1,5 +1,5 @@
-{% extends "base.html" %} {% block title %}Admin — AI Allucanget{% endblock %}
-{% block content %}
+{% extends "base.html" %} {% block title %}Admin — All You Can GET AI{% endblock
+%} {% block content %}
 <div class="card">
   <h1>Admin Dashboard</h1>