refactor: show confirm modal errors inline instead of global banner

feat: add loadingProducts flag and disable save button while loading

fix: read fresh reservoir on save to avoid stale isLocked

fix: race condition with productId init on new reservoir

fix: keep refresh button label on desktop and tablet

docs: add screenshots to README

fix: icon-only refresh button on mobile to prevent close btn overflow

feat: add vercel.json with build config and deploy instructions

fix: scrollbar, tablet gap, mobile touch targets & back btn

fix(ci): use npm install instead of npm ci

ci: add lint workflow

feat: responsive layout, status filter, custom scrollbar, burger menu

feat: responsive design — mobile drawer, tablet layout, adaptive form

fix: code review — error handling, labels, cleanup

feat: reservoir admin ui

feat: api layer, types and store

init: project scaffold