fetchData not wrapped in useCallback in GitGraphView

## Bug Description
In `GitGraphView.tsx:29`, `fetchData` is defined inline and used in a useEffect dependency. This causes unnecessary re-renders and re-fetches on every render.

## Location
`creedflow-desktop/src/components/git/GitGraphView.tsx:29`

## Severity
**Low** — Performance issue, not functional.

## Steps to Fix
1. Wrap `fetchData` in `useCallback` with proper dependencies