- Move magic strings from AuthProvider, MainLayout, and ThemeProvider to frontend/src/utils/constants.ts - Add STORAGE_KEY_AUTHENTICATED, STORAGE_KEY_SIDEBAR_COLLAPSED, and STORAGE_KEY_THEME constants with JSDoc descriptions - Update all three files to import and use centralized keys - Prevents key drift and typo regressions across the frontend Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>