feat: customizable mobile reading experience

- Backend: Chapter, ReadingProgress, ReadingSettings models
- Backend: Chapter API (TOC + content), progress tracking, settings CRUD
- Frontend: ReadingPage with chapter navigation
- Frontend: TableOfContents drawer
- Frontend: ReadingSettingsPanel (theme, font, size, orientation)
- Frontend: Custom hooks for settings, chapters, progress tracking
- CSS: Mobile-first reading view with sepia/dark/light/paper themes
- Route: /reader/:bookId reading view from book detail page
- Docs: 001-customizable-mobile-reading-experience.md

backend/apps/reader/views.py

@@ -0,0 +1,33 @@
+from rest_framework import permissions, status
+from rest_framework.decorators import api_view, permission_classes
+from rest_framework.request import Request
+from rest_framework.response import Response
+
+from apps.reader.models import ReadingSettings
+from apps.reader.serializers import ReadingSettingsSerializer
+
+
+@api_view(["GET", "PUT", "PATCH"])
+@permission_classes([permissions.IsAuthenticated])
+def reading_settings_view(request: Request) -> Response:
+    """Get or update the current user's reading settings.
+
+    GET  → return existing settings (auto-create defaults if missing)
+    PUT  → create or fully replace settings
+    PATCH → partial update
+    """
+    user = request.user
+    settings, created = ReadingSettings.objects.get_or_create(user=user)
+
+    if request.method == "GET":
+        serializer = ReadingSettingsSerializer(settings)
+        return Response(serializer.data)
+
+    if request.method == "PUT":
+        serializer = ReadingSettingsSerializer(settings, data=request.data)
+    elif request.method == "PATCH":
+        serializer = ReadingSettingsSerializer(settings, data=request.data, partial=True)
+
+    serializer.is_valid(raise_exception=True)
+    serializer.save()
+    return Response(serializer.data, status=status.HTTP_200_OK)