fix: stabilize useEffect dependency in CodeDashboard

[ivangarm]

I noticed that CodeDashboard has a useEffect with an empty dependency array that references loadSessions, but loadSessions is not wrapped in useCallback. This means:

1. loadSessions is recreated on every render, but the effect captures only the initial version (stale closure).
2. ESLint's react-hooks/exhaustive-deps rule would flag this as a missing dependency.

The fix wraps loadSessions in useCallback with an empty dependency array (it only references stable state setters), and adds loadSessions to the useEffect dependency array. This makes the hook lint-clean and ensures the interval always calls the latest version of the function.

Changes:

• Added useCallback to the React import
• Wrapped loadSessions in useCallback(async () => { ... }, [])
• Changed useEffect dependency from [] to [loadSessions]

Verified by reviewing the diff and confirming that setIsLoading, setError, and setSessions are all stable state setters from useState, so the empty dependency array on useCallback is correct.