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/.env.example

@@ -0,0 +1,17 @@
+# Application
+APP_NAME=Troubleshooting Decision Tree
+DEBUG=true
+
+# Database
+DATABASE_URL=postgresql+asyncpg://postgres:postgres@localhost:5432/decision_tree
+DATABASE_URL_SYNC=postgresql://postgres:postgres@localhost:5432/decision_tree
+
+# JWT Settings - CHANGE THESE IN PRODUCTION
+# Generate with: openssl rand -hex 32
+SECRET_KEY=your-super-secret-key-change-this-in-production
+ALGORITHM=HS256
+ACCESS_TOKEN_EXPIRE_MINUTES=15
+REFRESH_TOKEN_EXPIRE_DAYS=7
+
+# CORS
+CORS_ORIGINS=["http://localhost:3000","http://localhost:5173"]