Add presigned URL and file upload functionality

Implemented endpoints for generating presigned URLs and handling file uploads. Added corresponding test cases to ensure proper functionality and error handling. Updated the main router to include the new uploads API.

backend/app/api/router.py

@@ -3,8 +3,11 @@ from fastapi import APIRouter
 from app.api.routes import auth
 from app.api.routes import event_themes
 from app.api.routes.events import router as events
+from app.api.routes import uploads
 api_router = APIRouter()
 api_router.include_router(auth.router, prefix="/auth", tags=["auth"])
 api_router.include_router(event_themes.router, prefix="/event_themes", tags=["event_themes"])
 
 api_router.include_router(events.events_router, prefix="/events", tags=["events"])
+
+api_router.include_router(uploads.router, prefix="/uploads", tags=["uploads"])