feat: replace email flows with in-app notifications

Add recipient notification detail and filtering, a queued admin composer, and contextual automatic titles. Retire email delivery, obsolete auth routes, newsletter data, and related templates and settings.

templates/admin/users/send_notification.html

@@ -0,0 +1,17 @@
+{% extends "admin/base_site.html" %}
+{% block content %}
+<div dir="rtl">
+  <h1>ارسال اعلان برای {{ selected_count }} کاربر</h1>
+  {{ form.media }}
+  <form method="post">
+    {% csrf_token %}
+    {{ form.as_p }}
+    {% for user_id in selected_ids %}
+      <input type="hidden" name="{{ action_checkbox_name }}" value="{{ user_id }}">
+    {% endfor %}
+    <input type="hidden" name="action" value="send_notification">
+    <input type="hidden" name="index" value="0">
+    <button type="submit" name="confirm_send" value="1">ارسال اعلان</button>
+  </form>
+</div>
+{% endblock %}