Initial commit: Backend API Phase 1a complete

- FastAPI backend with JWT auth
- PostgreSQL database schema
- Trees and Sessions CRUD APIs
- Export functionality (Markdown, Text, HTML)
- Docker setup for local development
- Alembic migrations

backend/requirements.txt

@@ -0,0 +1,22 @@
+# FastAPI and server
+fastapi==0.109.2
+uvicorn[standard]==0.27.1
+
+# Database
+sqlalchemy==2.0.25
+asyncpg==0.29.0
+psycopg2-binary==2.9.9
+alembic==1.13.1
+
+# Authentication
+python-jose[cryptography]==3.3.0
+passlib[bcrypt]==1.7.4
+python-multipart==0.0.9
+
+# Validation and settings
+pydantic==2.6.1
+pydantic-settings==2.1.0
+email-validator==2.1.0
+
+# Utilities
+python-dotenv==1.0.1