Refactor back-end code

[StephanAkkerman]

1. Description:

   • Problem:
     The backend code is a bit of a mess right now. We are also misusing the pip install functionality right now to make it a package. The folder structure should be looked at and maybe some python files can be merged or moved.

   • Solution:
     Look into the file structure, the consequences of not using a pip package for the installation, renaming the directories and files, and more?

   • Prerequisites:
     [List any requirements or dependencies needed before starting.]

2. Tasks:

   • Remove pip installation
   • Redo file structure
   • Rename files
   • Group code
   • Rerun tests
   • Test all code

3. Additional context
   On request of @TimKoornstra

[StephanAkkerman]

@TimKoornstra Should we ask uithub or repo2txt for suggestions on file structure?

[TimKoornstra]

Something more like this for the file structure:

.
├── backend/
│   ├── requirements.txt       # Python dependencies
│   │
│   ├── fluentai/              # Your main application code
│   │   ├── __init__.py
│   │   ├── logger.py          # Logging setup
│   │   ├── api/
│   │   │   ├── __init__.py
│   │   │   ├── app.py         # FastAPI entry point
│   │   │   └── routes.py      # API routes
│   │   ├── constants/
│   │   │   ├── __init__.py
│   │   │   ├── config.py
│   │   │   └── languages.py
│   │   ├── services/
│   │   │   ├── imagine/
│   │   │   │   ├── __init__.py
│   │   │   │   ├── image_gen.py
│   │   │   │   └── verbal_cue_gen.py
│   │   │   ├── mnemonic/
│   │   │   │   ├── ...
│   │   │   ├── tts/
│   │   │   │   ├── fallback.py
│   │   │   │   └── tts.py
│   │   │   └── ...
│   │   ├── utils/
│   │   │   ├── __init__.py
│   │   │   ├── fasttext.py
│   │   │   └── model_loader.py
│   │   └── data/
│   │       ├── g2p-to-tss-mapping.parquet
│   │       ├── languages.json
│   │       ├── config.yaml
│   │       └── tts-languages.parquet
│   │
│   └── tests/                  # Root-level tests directory
│       ├── __init__.py
│       ├── test_api/           # Test FastAPI endpoints
│       │   ├── __init__.py
│       │   ├── test_routes.py
│       ├── test_services/      # Test backend services
│       │   ├── __init__.py
│       │   ├── test_imagine.py
│       │   ├── test_tts.py
│       │   └── ...
│       └── test_utils.py       # Test general utilities
├── frontend
│   └── ...               # Your Next.js application
├── .github
│   └── ...               # GitHub Actions, Issue templates
├── .gitignore
├── CONTRIBUTING.md
├── LICENSE
├── README.md