feat(web): add React error boundaries and Next.js error.tsx fallbacks

Runtime errors in components now show a friendly "Something went wrong"
screen instead of a white page. Timeline and staffing panel are
individually wrapped. Route-level error.tsx handles server component errors.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/src/app/(app)/timeline/page.tsx

@@ -1,4 +1,5 @@
 import dynamic from "next/dynamic";
+import { ErrorBoundary } from "~/components/ui/ErrorBoundary.js";
 
 const TimelineView = dynamic(
   () => import("~/components/timeline/TimelineView.js").then((m) => m.TimelineView),
@@ -22,7 +23,9 @@ export default function TimelinePage() {
           <p className="app-page-subtitle mt-1">Interactive resource planning timeline</p>
         </div>
       </div>
-      <TimelineView />
+      <ErrorBoundary>
+        <TimelineView />
+      </ErrorBoundary>
     </div>
   );
 }