added api directory to Dockerfile for backend application

Fix: Next.js bind to 0.0.0.0 for container internal access

..

Implement multi-stage Docker build for Next.js frontend and Python backend; add frontend proxy in FastAPI to handle requests, and remove old cleanup task functionality.

Initial commit of the Ad Generator Lite project, including backend services, frontend components, and configuration files. Added core functionalities for ad generation, user management, and image processing, along with a structured matrix system for ad testing.