feat: monorepo structure with Django backend, React frontend, and Expo mobile app

- Backend: Django 5 + DRF with accounts, documents, collections, and reading apps
  - Custom User model with email-based auth, JWT via SimpleJWT
  - Full CRUD viewsets with ModelSerializer + DRF routers
  - pytest, Ruff, drf-spectacular (OpenAPI), whitenoise
  - Dockerfile for production deployment

- Frontend: React 18 + TypeScript + Vite
  - Lazy-loaded routes with ProtectedRoute/PublicRoute guards
  - Auth context with useReducer, token refresh interceptor
  - Pages: Login, Register, Library, Document Detail, Reader, Collections, Settings
  - Dark theme, responsive grid layout, Vite proxy to Django backend

- Mobile: Expo SDK 51 + React Native + Expo Router
  - File-based routing with login, register, and library screens
  - AsyncStorage for token persistence, token refresh interceptor
  - Shared API types via @cloud-reader/shared workspace package

- Shared: TypeScript types (API responses, auth, documents, etc.)
- CI/CD: 3 independent GitHub Actions pipelines (backend, frontend, mobile)

frontend/Dockerfile

@@ -0,0 +1,20 @@
+FROM node:20-alpine AS build
+
+WORKDIR /app
+
+COPY package.json yarn.lock ./
+COPY shared/package.json shared/
+COPY frontend/package.json frontend/
+
+RUN yarn install --frozen-lockfile
+
+COPY shared/ shared/
+COPY frontend/ frontend/
+
+RUN yarn workspace @cloud-reader/shared build && \
+    yarn workspace @cloud-reader/frontend build
+
+FROM nginx:alpine
+COPY --from=build /app/frontend/dist /usr/share/nginx/html
+COPY frontend/nginx.conf /etc/nginx/conf.d/default.conf
+EXPOSE 80