Add foundational user authentication and registration system

Introduces schemas for user management, token handling, and password hashing. Implements routes for user registration, login, token refresh, and user info retrieval. Sets up authentication dependencies and integrates the API router with the application.

backend/app/main.py

@@ -3,7 +3,7 @@ from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import HTMLResponse
 
 from app.core.config import settings
-
+from app.api.main import api_router
 import logging
 
 logger = logging.getLogger(__name__)
@@ -39,3 +39,5 @@ async def root():
         </body>
     </html>
     """
+
+app.include_router(api_router, prefix=settings.API_V1_STR)