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

backend/apps/books/admin.py

@@ -0,0 +1,9 @@
+from django.contrib import admin
+
+from apps.books.models import Book
+
+
+@admin.register(Book)
+class BookAdmin(admin.ModelAdmin):
+    list_display = ("title", "author", "total_pages", "created_at")
+    search_fields = ("title", "author")

backend/apps/books/apps.py

@@ -0,0 +1,7 @@
+from django.apps import AppConfig
+
+
+class BooksConfig(AppConfig):
+    default_auto_field = "django.db.models.BigAutoField"
+    name = "apps.books"
+    label = "books"

backend/apps/books/models.py

@@ -0,0 +1,21 @@
+from django.db import models
+
+
+class Book(models.Model):
+    """Represents a book in the user's library."""
+
+    title = models.CharField(max_length=512)
+    author = models.CharField(max_length=256, blank=True, default="")
+    total_pages = models.PositiveIntegerField(default=0)
+    cover_image = models.URLField(blank=True, default="")
+    created_at = models.DateTimeField(auto_now_add=True)
+    updated_at = models.DateTimeField(auto_now=True)
+
+    class Meta:
+        db_table = "books_book"
+        verbose_name = "Book"
+        verbose_name_plural = "Books"
+        ordering = ["title"]
+
+    def __str__(self) -> str:
+        return self.title

backend/apps/books/serializers.py

@@ -0,0 +1,28 @@
+from rest_framework import serializers
+
+from apps.books.models import Book
+
+
+class BookSerializer(serializers.ModelSerializer):
+    """Serialize Book data."""
+
+    class Meta:
+        model = Book
+        fields = [
+            "id",
+            "title",
+            "author",
+            "total_pages",
+            "cover_image",
+            "created_at",
+            "updated_at",
+        ]
+        read_only_fields = ["id", "created_at", "updated_at"]
+
+
+class BookListSerializer(serializers.ModelSerializer):
+    """Lightweight serializer for list views (excludes heavy fields)."""
+
+    class Meta:
+        model = Book
+        fields = ["id", "title", "author", "total_pages", "cover_image"]

backend/apps/books/urls.py

@@ -0,0 +1,11 @@
+from django.urls import include, path
+from rest_framework.routers import DefaultRouter
+
+from apps.books.views import BookViewSet
+
+router = DefaultRouter()
+router.register(r"", BookViewSet, basename="book")
+
+urlpatterns = [
+    path("", include(router.urls)),
+]

backend/apps/books/views.py

@@ -0,0 +1,24 @@
+from django_filters.rest_framework import DjangoFilterBackend
+from rest_framework import viewsets
+from rest_framework.filters import OrderingFilter, SearchFilter
+from rest_framework.permissions import IsAuthenticated
+
+from apps.books.models import Book
+from apps.books.serializers import BookListSerializer, BookSerializer
+
+
+class BookViewSet(viewsets.ModelViewSet):
+    """CRUD for books."""
+
+    queryset = Book.objects.all()
+    permission_classes = [IsAuthenticated]
+    filter_backends = [DjangoFilterBackend, SearchFilter, OrderingFilter]
+    filterset_fields = ["author"]
+    search_fields = ["title", "author"]
+    ordering_fields = ["title", "author", "created_at"]
+    ordering = ["title"]
+
+    def get_serializer_class(self):
+        if self.action == "list":
+            return BookListSerializer
+        return BookSerializer