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/config/django.py

@@ -0,0 +1,153 @@
+"""
+Django settings for cloud-reader backend.
+
+Generated using Django 5.1.  Customised with pydantic-settings integration.
+"""
+
+from pathlib import Path
+
+from config.settings import settings
+
+# ---------------------------------------------------------------------------
+# Build paths
+# ---------------------------------------------------------------------------
+BASE_DIR = Path(__file__).resolve().parent.parent
+
+# ---------------------------------------------------------------------------
+# Security
+# ---------------------------------------------------------------------------
+SECRET_KEY = settings.DJANGO_SECRET_KEY
+DEBUG = settings.DJANGO_DEBUG
+ALLOWED_HOSTS = settings.DJANGO_ALLOWED_HOSTS
+
+# ---------------------------------------------------------------------------
+# Application definition
+# ---------------------------------------------------------------------------
+INSTALLED_APPS = [
+    # Django built-in
+    "django.contrib.admin",
+    "django.contrib.auth",
+    "django.contrib.contenttypes",
+    "django.contrib.sessions",
+    "django.contrib.messages",
+    "django.contrib.staticfiles",
+    # Third-party
+    "rest_framework",
+    "rest_framework_simplejwt",
+    "corsheaders",
+    "django_filters",
+    # Local apps
+    "apps.users",
+    "apps.books",
+    "apps.annotations",
+]
+
+MIDDLEWARE = [
+    "corsheaders.middleware.CorsMiddleware",
+    "django.middleware.security.SecurityMiddleware",
+    "django.contrib.sessions.middleware.SessionMiddleware",
+    "django.middleware.common.CommonMiddleware",
+    "django.middleware.csrf.CsrfViewMiddleware",
+    "django.contrib.auth.middleware.AuthenticationMiddleware",
+    "django.contrib.messages.middleware.MessageMiddleware",
+    "django.middleware.clickjacking.XFrameOptionsMiddleware",
+]
+
+ROOT_URLCONF = "config.urls"
+
+TEMPLATES = [
+    {
+        "BACKEND": "django.template.backends.django.DjangoTemplates",
+        "DIRS": [],
+        "APP_DIRS": True,
+        "OPTIONS": {
+            "context_processors": [
+                "django.template.context_processors.debug",
+                "django.template.context_processors.request",
+                "django.contrib.auth.context_processors.auth",
+                "django.contrib.messages.context_processors.messages",
+            ],
+        },
+    },
+]
+
+WSGI_APPLICATION = "config.wsgi.application"
+
+# ---------------------------------------------------------------------------
+# Database
+# ---------------------------------------------------------------------------
+DATABASES = {
+    "default": {
+        "ENGINE": "django.db.backends.postgresql",
+        "NAME": settings.DB_NAME,
+        "USER": settings.DB_USER,
+        "PASSWORD": settings.DB_PASSWORD,
+        "HOST": settings.DB_HOST,
+        "PORT": settings.DB_PORT,
+    }
+}
+
+# ---------------------------------------------------------------------------
+# Auth
+# ---------------------------------------------------------------------------
+AUTH_USER_MODEL = "users.User"
+
+AUTH_PASSWORD_VALIDATORS = [
+    {"NAME": "django.contrib.auth.password_validation.MinimumLengthValidator"},
+    {"NAME": "django.contrib.auth.password_validation.NumericPasswordValidator"},
+]
+
+# ---------------------------------------------------------------------------
+# DRF
+# ---------------------------------------------------------------------------
+REST_FRAMEWORK = {
+    "DEFAULT_AUTHENTICATION_CLASSES": (
+        "rest_framework_simplejwt.authentication.JWTAuthentication",
+    ),
+    "DEFAULT_PERMISSION_CLASSES": (
+        "rest_framework.permissions.IsAuthenticated",
+    ),
+    "DEFAULT_PAGINATION_CLASS": "rest_framework.pagination.PageNumberPagination",
+    "PAGE_SIZE": 50,
+    "DEFAULT_FILTER_BACKENDS": [
+        "django_filters.rest_framework.DjangoFilterBackend",
+        "rest_framework.filters.OrderingFilter",
+        "rest_framework.filters.SearchFilter",
+    ],
+}
+
+# ---------------------------------------------------------------------------
+# SimpleJWT
+# ---------------------------------------------------------------------------
+from datetime import timedelta
+
+SIMPLE_JWT = {
+    "ACCESS_TOKEN_LIFETIME": timedelta(minutes=settings.JWT_ACCESS_TOKEN_LIFETIME_MINUTES),
+    "REFRESH_TOKEN_LIFETIME": timedelta(days=settings.JWT_REFRESH_TOKEN_LIFETIME_DAYS),
+}
+
+# ---------------------------------------------------------------------------
+# CORS
+# ---------------------------------------------------------------------------
+CORS_ALLOWED_ORIGINS = settings.CORS_ALLOWED_ORIGINS
+
+# ---------------------------------------------------------------------------
+# i18n
+# ---------------------------------------------------------------------------
+LANGUAGE_CODE = "en-us"
+TIME_ZONE = "UTC"
+USE_I18N = True
+USE_TZ = True
+
+# ---------------------------------------------------------------------------
+# Static / Media
+# ---------------------------------------------------------------------------
+STATIC_URL = "static/"
+STATIC_ROOT = BASE_DIR / "staticfiles"
+MEDIA_URL = "media/"
+MEDIA_ROOT = BASE_DIR / "media"
+
+# ---------------------------------------------------------------------------
+# Default primary key
+# ---------------------------------------------------------------------------
+DEFAULT_AUTO_FIELD = "django.db.models.BigAutoField"