Add admin features, user profile management, and generation capabilities

- Implemented admin dashboard with user management features including role assignment and deletion.
- Added user profile page for updating email and password.
- Created separate routes and templates for text, image, and video generation with appropriate forms.
- Enhanced navigation with dropdown for generation options and loading overlay for better user experience.
- Introduced comprehensive error handling and user feedback through alerts.
- Updated styles for improved UI consistency and responsiveness.

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

frontend/app/templates/generate_text.html

@@ -0,0 +1,35 @@
+{% extends "base.html" %}
+{% block title %}Text Generation — AI Allucanget{% endblock %}
+{% block content %}
+<div class="card">
+  <h1>Text Generation</h1>
+  <form method="post">
+    <label for="model">Model</label>
+    <input id="model" name="model" type="text" required
+           placeholder="e.g. openai/gpt-4o"
+           value="{{ request.form.get('model', '') }}">
+
+    <label for="prompt">Prompt</label>
+    <textarea id="prompt" name="prompt" rows="5" required
+              placeholder="Describe what you want…">{{ request.form.get('prompt', '') }}</textarea>
+
+    <button type="submit">Generate text</button>
+  </form>
+
+  {% if error %}
+    <div class="alert alert-error mt-2">{{ error }}</div>
+  {% endif %}
+
+  {% if result %}
+    <div class="result">
+      <h2>Result</h2>
+      <pre>{{ result.content }}</pre>
+      {% if result.usage %}
+        <p class="text-muted mt-1" style="font-size:0.8rem;">
+          Tokens: {{ result.usage.get('total_tokens', '—') }}
+        </p>
+      {% endif %}
+    </div>
+  {% endif %}
+</div>
+{% endblock %}