feat: #345 even if the backend data returns empty, the skeleton of the chart will be displayed. (#461)

… chart will be displayed.

### What problem does this PR solve?

feat: #345 even if the backend data returns empty, the skeleton of the
chart will be displayed.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

### What problem does this PR solve?

feat: render stats charts
feat: create api token
feat: delete api token
feat: add ChatApiKeyModal
feat: add RagLineChart


Issue link: #345

### Type of change

- [x] New Feature (non-breaking change which adds functionality)