Response time chart is empty

**Describe the bug**
The response time charts are empty for all of my monitors. Peekaping version v0.0.39

**Database**
- postgresql

**To Reproduce**
Happens for both existing and new monitors

**Expected behavior**
plot the response times

**Screenshots**

**Desktop (please complete the following information):**
- OS: Win20
- Browser Firefox
- Version 143.0.1

**Additional context**
No errors in the container log or the browser console

The issue is about empty response time charts in the monitoring UI. Start by examining the data collection and aggregation logic for response times, likely in a service or handler file. Check the chart rendering component in the frontend and the API endpoint that serves the chart data. Verify the database queries for response time metrics in PostgreSQL. Look for any recent changes in version v0.0.39 that might have broken the data flow or chart rendering.

Rédigé par le modèle d'indexation à partir du texte de l'issue.