feat: notifications inbox page

The bell only ever showed the last 30; add a full paginated /notifications
page, per-notification mark-read, and a shared notificationHref helper so
the bell and the page route identically instead of duplicating the logic.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/app/(app)/notifications/loading.tsx

@@ -0,0 +1,14 @@
+import { PageHeaderSkeleton, ListRowSkeleton } from "@/components/shared/skeletons";
+
+export default function NotificationsLoading() {
+  return (
+    <div className="space-y-6 max-w-2xl">
+      <PageHeaderSkeleton actions={1} />
+      <div className="space-y-3">
+        {Array.from({ length: 6 }).map((_, i) => (
+          <ListRowSkeleton key={i} />
+        ))}
+      </div>
+    </div>
+  );
+}