Add models caching and management functionality with corresponding API endpoints and templates

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

frontend/app/templates/generate_text.html

@@ -4,6 +4,13 @@ AI{% endblock %} {% block content %}
   <h1>Text Generation</h1>
   <form method="post">
     <label for="model">Model</label>
+    {% if models %}
+    <select id="model" name="model" required>
+      {% for m in models %}
+      <option value="{{ m.id }}" {% if request.form.get('model', '') == m.id %}selected{% endif %}>{{ m.name }}</option>
+      {% endfor %}
+    </select>
+    {% else %}
     <input
       id="model"
       name="model"
@@ -12,6 +19,7 @@ AI{% endblock %} {% block content %}
       placeholder="e.g. openai/gpt-4o"
       value="{{ request.form.get('model', '') }}"
     />
+    {% endif %}
 
     <label for="prompt">Prompt</label>
     <textarea