Resolve backend Qodana critical and high findings (#314)

Resolve recommended-profile Critical and High findings, retain narrow analyzer exceptions, and update the edge-broker WebSocket dependency to a non-vulnerable release.

config.example.php

@@ -31,7 +31,7 @@ $MINIO = [
     'access_key' => '', // Minio access
     'secret_key' => '' // Minio secret key
 ];
-$SLACK_DEFAULT_WEBHOOK = ''; // Default Slack webhook URL e.g. https://hooks.slack.com/services/XXXXXXXXX/XXXXXXXXX/XXXXXXXXXXXXXXXXXXXXXXXX
+$SLACK_DEFAULT_WEBHOOK = ''; // Set through SLACK_DEFAULT_WEBHOOK; never commit a production webhook URL.
 $REDIS_CONFIG = [
     'host' => '', // Redis host (IP address)
     'user' => '', // Redis user