feat: bookmarks and notes management

- Backend: Django REST Framework API with Bookmark and Note models
  - ViewSets with user-scoped querysets and select_related for N+1 prevention
  - Create/List/Detail/Update/Delete endpoints
  - Batch delete operations
  - Unique constraint on user+book+page for bookmarks
  - IsOwner permission class for object-level access control
  - Full serializer validation (page > 0, non-empty content, duplicate check)
  - 30+ pytest-django tests covering CRUD, auth, filtering, edge cases

- Frontend: React TypeScript components
  - AnnotationsContext with useReducer for state management
  - BookmarkList, NoteList, AddAnnotationForm, AnnotationsDashboard
  - Inline note editing with immediate save
  - Batch delete support
  - API client with JWT auto-refresh interceptors
  - Paginated query hook for infinite scroll support
  - Responsive CSS with loading/empty states

- Infrastructure: Django project with custom User model, JWT auth, CORS
  - PostgreSQL database models with proper FK and indexes
  - Django admin configuration for all models

frontend/src/components/layout/Layout.tsx

@@ -0,0 +1,27 @@
+import React from "react";
+import { AnnotationsProvider } from "@/context/AnnotationsContext";
+
+interface LayoutProps {
+  children: React.ReactNode;
+  title?: string;
+}
+
+export function Layout({
+  children,
+  title = "Cloud Reader",
+}: LayoutProps): React.ReactElement {
+  return (
+    <AnnotationsProvider>
+      <div className="app-container">
+        <header className="app-header">
+          <h1 className="app-title">{title}</h1>
+          <nav className="app-nav">
+            <a href="/" className="nav-link">Home</a>
+            <a href="/bookmarks-notes" className="nav-link">Bookmarks & Notes</a>
+          </nav>
+        </header>
+        <main className="app-main">{children}</main>
+      </div>
+    </AnnotationsProvider>
+  );
+}