add backend source code

backend/requirements.txt

@@ -0,0 +1,16 @@
+fastapi>=0.115.0
+uvicorn[standard]>=0.32.0
+python-multipart>=0.0.9
+sqlalchemy>=2.0.36
+aiosqlite>=0.19.0
+asyncpg>=0.30.0
+alembic>=1.14.0
+pydantic>=2.10.0
+pydantic-settings>=2.6.0
+email-validator>=2.2.0
+python-jose[cryptography]>=3.3.0
+passlib[bcrypt]>=1.7.4
+python-dotenv>=1.0.0
+httpx>=0.28.0
+pytest>=8.0.0
+pytest-asyncio>=0.24.0