Polish Today dashboard loading, errors, and layout (Phase 4).

Add section error boundaries, retry banner with stale-while-revalidate, shared skeletons, responsive action layout, and org-switch refetching.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/components/today/TodayLoadErrorBanner.tsx

@@ -0,0 +1,33 @@
+'use client';
+
+import { Button } from '@/components/ui/shared/Button';
+
+interface TodayLoadErrorBannerProps {
+  message: string;
+  retryLabel: string;
+  onRetry: () => void;
+  isRetrying?: boolean;
+}
+
+export function TodayLoadErrorBanner({
+  message,
+  retryLabel,
+  onRetry,
+  isRetrying = false,
+}: TodayLoadErrorBannerProps) {
+  return (
+    <div className="rounded-[var(--radius-md)] border border-badge-danger-border bg-badge-danger-bg/40 p-4 flex flex-col sm:flex-row sm:items-center sm:justify-between gap-3">
+      <p className="text-sm text-badge-danger-fg">{message}</p>
+      <Button
+        type="button"
+        variant="outline"
+        size="sm"
+        onClick={onRetry}
+        isLoading={isRetrying}
+        className="shrink-0 border-badge-danger-border text-badge-danger-fg hover:bg-badge-danger-bg/30"
+      >
+        {retryLabel}
+      </Button>
+    </div>
+  );
+}