refactor: extract shared utils/components, split requests page data into hook
- Create frontend/src/lib/shared/ with formatters, userUtils, paginationUtils
(formatDate, formatMoney, displayUserName, userProfileLink, extractNextPage, loadAllPages)
- Create frontend/src/components/shared/SearchableSelect.tsx
(SearchableSelectSingle + SearchableSelectMulti, replaces 3 inline copies)
- Extract requests page data/state/actions into useRequestsPage hook
(requests/page.tsx: 1580 → ~280 lines of pure JSX)
- Replace duplicated helpers in equipment/page.tsx with shared imports
(~80 lines removed: formatDate, formatMoney, displayUserName, extractNextPage,
loadAllPages, inline SearchableSelectSingle)
- Replace duplicated helpers in procurement/page.tsx with shared imports
(~90 lines removed: fmt, money, displayUserName, extractNextPage,
inline departments loader, inline SearchableSelectSingle)
- 609 backend tests pass, TypeScript typecheck clean, ESLint clean
0a80eb86cf