refactor: update startup command to use app.py instead of uvicorn and add HF_TOKEN note to documentation

Dockerfile

@@ -10,4 +10,4 @@ COPY . .
 ENV STEP_ZERO_MOCK=1
 EXPOSE 7860
 
-CMD ["uvicorn", "app:app", "--host", "0.0.0.0", "--port", "7860"]
+CMD ["python", "app.py"]

README.md

@@ -23,10 +23,8 @@ The resulting fine-tuned model and synthetic dataset from this project have been
 ## Quick Start (Mock Mode)
 
 ```bash
-python3 -m venv .venv
-. .venv/bin/activate
 python -m pip install -r requirements.txt
-uvicorn app:app --host 0.0.0.0 --port 7860
+python app.py
 ```
 
 Open `http://localhost:7860`.
@@ -46,9 +44,11 @@ Then run:
 STEP_ZERO_MOCK=0 \
 NEMOTRON_MODEL_PATH=./models/step-zero-nemotron-finetuned.gguf \
 MINICPM_MODEL_PATH=./models/minicpm-3-4b.gguf \
-uvicorn app:app --host 0.0.0.0 --port 7860
+python app.py
 ```
 
+> **Note on "Sharing is Caring" Badge:** If you wish to use the "Push to Hub" button to export your trace to Hugging Face, ensure you have exported your `HF_TOKEN` environment variable before running the app.
+
 ## Modal Fine-Tuning Pipeline
 
 If you want to reproduce the Nemotron fine-tuning run: