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>

services/frontend/src/features/dashboard/components/UserSummaryList.tsx

@@ -1,7 +1,7 @@
 import { User } from "lucide-react";
 import type { DashboardUser } from "../../../shared/api/client";
-import { SummaryList } from "../../../shared/ui";
 import type { SummaryItem } from "../../../shared/ui";
+import { SummaryList } from "../../../shared/ui";
 
 interface UserSummaryListProps {
   users: DashboardUser[];