fix: update grok default model to grok-2

Changed grok-beta to grok-2 across backend config, dashboard tests, and frontend monitoring.

static/js/pages/monitoring.js

@@ -492,7 +492,7 @@ class MonitoringPage {
     simulateRequest() {
         const clients = ['client-1', 'client-2', 'client-3', 'client-4', 'client-5'];
         const providers = ['OpenAI', 'Gemini', 'DeepSeek', 'Grok'];
-        const models = ['gpt-4', 'gpt-3.5-turbo', 'gemini-pro', 'deepseek-chat', 'grok-beta'];
+        const models = ['gpt-4o', 'gpt-4o-mini', 'gemini-2.0-flash', 'deepseek-chat', 'grok-2'];
         const statuses = ['success', 'success', 'success', 'error', 'warning']; // Mostly success
         
         const request = {