Fixes#7
- Add frontend/src/lib/auth.tsx with AuthProvider and useAuth hook
- Add frontend/src/lib/api.ts with chat, getKBStats, listDocuments, etc.
- Add frontend/src/lib/filePicker.ts with path utilities
- Update .gitignore to not ignore frontend/src/lib/
These files were imported but never committed, preventing fresh
installations from building the frontend.
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Co-Authored-By: Claude <noreply@anthropic.com>
