Implement Docker setup for Beatstep API and frontend

Commit notes

- Added Dockerfile and docker-compose.yml for containerized development environment. - Created .dockerignore to exclude unnecessary files from Docker context. - Introduced DOCKER_SETUP.md for comprehensive setup instructions. - Established Makefile for simplified build and run commands. - Removed Firebase-related files and references to streamline the project towards a Go-based backend. - Updated package.json to reflect changes in dependencies and removed Firebase integration. - Refactored authentication context to utilize a new AuthProvider for user management.