feat: show notification source (agent vs SAC) in alerts and reports

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

backend/tests/test_daily_report.py

@@ -247,7 +247,9 @@ def test_daily_report_telegram_html_uses_report_html(db_session):
         details={"report_html": "<b>📊 OK</b><br>line"},
         payload={},
     )
-    assert format_event_telegram_html(event) == "<b>📊 OK</b>\nline"
+    assert format_event_telegram_html(event) == (
+        "<b>📊 OK</b>\nline\n📡 Оповещение: агент (ssh-monitor)"
+    )
 
 
 def test_sanitize_telegram_html_strips_div_and_br():