add server: FastAPI + Docker

Python 3.11 + FastAPI con tre endpoint (/health, /auth/test, /recipes/generate).
Autenticazione via header X-App-Password, validazione input Pydantic,
chiamata in streaming a NVIDIA NIM (nemotron-3-ultra-550b-a55b) con thinking.
Dockerizzato con docker-compose; configurazione tramite .env.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/Dockerfile

@@ -0,0 +1,7 @@
+FROM python:3.11-slim
+WORKDIR /app
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+COPY app/ ./app/
+EXPOSE 8000
+CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]