Add user auth, personal cabinet, admin panel and first admin bootstrap

Co-authored-by: Cursor <cursoragent@cursor.com>

app/templates/partials/alerts.html

@@ -0,0 +1,9 @@
+{% with messages = get_flashed_messages(with_categories=true) %}
+{% if messages %}
+<section class="container alerts">
+    {% for category, message in messages %}
+    <div class="alert alert--{{ category }}">{{ message }}</div>
+    {% endfor %}
+</section>
+{% endif %}
+{% endwith %}