Add CLAUDE.md for Claude Code guidance

Add comprehensive documentation file to help future Claude instances understand:
- Essential commands for development, testing, and deployment
- High-level architecture patterns for both backend and frontend
- Database migration workflow
- Authentication flow details
- Development environment URLs

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: User

CLAUDE.md

@@ -0,0 +1,123 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Full-stack FastAPI + React application with:
+- **Backend**: FastAPI, SQLModel, PostgreSQL, Alembic, JWT auth
+- **Frontend**: React, TypeScript, Vite, TanStack Query/Router, Chakra UI
+- **Infrastructure**: Docker Compose, Traefik proxy
+
+## Essential Commands
+
+### Backend Development
+```bash
+# Run tests
+cd backend && bash ./scripts/test.sh
+
+# Run specific test
+cd backend && python -m pytest app/tests/api/routes/test_users.py::test_read_users -xvs
+
+# Lint code
+cd backend && bash ./scripts/lint.sh
+
+# Format code
+cd backend && bash ./scripts/format.sh
+
+# Create migration
+cd backend && alembic revision -m "migration_name" --autogenerate
+
+# Apply migrations
+cd backend && alembic upgrade head
+
+# Database setup
+cd backend && bash ./scripts/setup_db.sh
+```
+
+### Frontend Development
+```bash
+# Install dependencies
+cd frontend && npm install
+
+# Run development server
+cd frontend && npm run dev
+
+# Build for production
+cd frontend && npm run build
+
+# Lint/format code
+cd frontend && npm run lint
+
+# Generate API client from OpenAPI
+cd frontend && npm run generate-client
+
+# Run E2E tests
+cd frontend && npx playwright test
+
+# Run specific test
+cd frontend && npx playwright test tests/login.spec.ts
+```
+
+### Docker Development
+```bash
+# Start all services
+docker compose up -d
+
+# View logs
+docker compose logs -f backend
+
+# Rebuild specific service
+docker compose build backend
+
+# Run backend tests in Docker
+docker compose exec backend bash /app/scripts/test.sh
+
+# Access database
+docker compose exec db psql -U postgres app
+```
+
+## Architecture Patterns
+
+### Backend Structure
+- **Models**: SQLModel with UUID primary keys and timestamp mixins (`app/models/`)
+- **Routes**: Modular route organization (`app/api/routes/`)
+- **Auth**: JWT with refresh tokens, OAuth support (`app/api/routes/auth/`)
+- **Config**: Pydantic Settings (`app/core/config.py`)
+- **Database**: Async SQLAlchemy sessions (`app/db/session.py`)
+
+### Frontend Structure
+- **Routing**: File-based routing with TanStack Router (`src/routes/`)
+- **API Client**: Auto-generated from OpenAPI (`src/client/`)
+- **Auth**: Token management in localStorage (`src/hooks/useAuth.ts`)
+- **Components**: Organized by feature (`src/components/`)
+- **UI**: Chakra UI with custom theme (`src/theme.tsx`)
+
+### Database Migrations
+Alembic manages migrations. When modifying models:
+1. Make changes to SQLModel classes
+2. Generate migration: `alembic revision -m "description" --autogenerate`
+3. Review generated migration file
+4. Apply: `alembic upgrade head`
+
+### Authentication Flow
+- Login returns access and refresh tokens
+- Access token expires in 15 minutes
+- Refresh token used to get new access token
+- Frontend automatically refreshes tokens
+
+## Development URLs
+- Frontend: http://localhost:5173
+- Backend API: http://localhost:8000
+- API Docs: http://localhost:8000/docs
+- Adminer (DB UI): http://localhost:8080
+- MailCatcher: http://localhost:1080
+- Traefik Dashboard: http://localhost:8090
+
+## Environment Variables
+Create `.env` file from template. Key variables:
+- `POSTGRES_*`: Database connection
+- `FIRST_SUPERUSER*`: Initial admin account
+- `BACKEND_CORS_ORIGINS`: CORS configuration
+- `SMTP_*`: Email settings
+- `VITE_API_URL`: Frontend API endpoint