feat: add subtle creator attribution

- HTML comment in base.html with project description and link
- Small fixed footer in bottom-right corner: Crafted by mycloud24
- Footer styled to be unobtrusive (low opacity, small font)

app/templates/base.html

@@ -1,4 +1,9 @@
 <!DOCTYPE html>
+<!--
+    InviteMe — система управления приглашениями на мероприятия.
+    Создано с вниманием к деталям.
+    https://mycloud24.ru
+-->
 <html lang="ru">
 <head>
     <meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="csrf-token" content="{{ csrf_token() }}">
@@ -46,4 +51,5 @@
 {% block content %}{% endblock %}</main>
 {% if current_user %}</section></div>{% endif %}
 <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/js/bootstrap.bundle.min.js" integrity="sha384-C6RzsynM9kWDrMNeT87bh95OGNyZPhcTNXj1NW7RuBCsyN/o0jlpcV8Qyq46cDfL" crossorigin="anonymous"></script><script src="{{ url_for('static', filename='js/app.js') }}"></script>{% block scripts %}{% endblock %}
+<footer class="app-footer" aria-hidden="true"><span>Crafted by <a href="https://mycloud24.ru" rel="noopener">mycloud24</a></span></footer>
 </body></html>