refactor(fe): DRY components, hooks, a11y fixes, and WS/client improvements
- Extract StatusBadge, SummaryList, ProfileDetail shared components (~300 lines deduplicated)
- Extract usePaginatedList<T>, useItemDetail<T> generic hooks (~170 lines deduplicated)
- Fix a11y: Badge (role=status, dark variants), Button (aria-disabled, motion-safe), Input (aria-invalid, errorId), Select (error variant), Skeleton (aria-hidden), MobileTabBar (full tab ARIA), Toast (timer leak fix, role=alert, keyboard dismiss), Card (role=region)
- Fix API client: buildSearchParams helper, request timeout, password caching, named types
- Fix WS: typed 24 event payloads (was all unknown), exponential backoff reconnect, max 20 attempts, msg.data guard
- Fix bug: listDashboardChannels cursor pagination was silently dropped
- Remove duplicate shimmer keyframes from tailwind.config.js
- Fix WaveformPlayer non-null assertion
Co-Authored-By: Claude <noreply@anthropic.com>
