refactor(notifications): rename test notification proxy function

Rename the `proxy_send_test_notification` function to `send_test_notification_proxy` for better naming consistency.

The corresponding template is updated to use `url_for` for the fetch request, making the URL generation more robust and maintainable.

app.py

@@ -121,7 +121,7 @@ def proxy_save_subscription():
         return jsonify({"error": str(e)}), 502
 
 @app.route('/send-test-notification', methods=['POST'])
-def proxy_send_test_notification():
+def send_test_notification_proxy():
     """Proxies the request to send a test notification to the backend."""
     if not session.get("logged_in"):
         return jsonify({'error': 'Unauthorized'}), 401

templates/base.html

@@ -68,7 +68,7 @@
 
             document.getElementById('version-link').addEventListener('click', function(event) {
                 event.preventDefault();
-                fetch('/send-test-notification', {
+                fetch('{{ url_for("send_test_notification_proxy") }}', {
                     method: 'POST'
                 }).then(response => response.json())
                   .then(data => console.log(data.message))