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/app/main.py

@@ -0,0 +1,110 @@
+import json
+import logging
+from contextlib import asynccontextmanager
+
+from fastapi import Depends, FastAPI, HTTPException, Header
+from fastapi.middleware.cors import CORSMiddleware
+from openai import AsyncOpenAI
+
+from .config import settings
+from .models import RecipeRequest, RecipeResponse
+from .prompt import SYSTEM_PROMPT
+
+logger = logging.getLogger("uvicorn")
+
+_client: AsyncOpenAI | None = None
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    global _client
+    _client = AsyncOpenAI(
+        api_key=settings.nvidia_api_key,
+        base_url=settings.nvidia_base_url,
+        timeout=float(settings.nvidia_timeout_seconds),
+    )
+    yield
+    await _client.close()
+
+
+app = FastAPI(title="Recipe AI Server", lifespan=lifespan)
+
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+
+def _check_password(x_app_password: str = Header(...)):
+    if x_app_password != settings.app_password:
+        raise HTTPException(status_code=401, detail="Password non valida")
+
+
+@app.get("/health")
+async def health():
+    return {"status": "ok", "provider": "nvidia", "model": settings.nvidia_model}
+
+
+@app.post("/auth/test", dependencies=[Depends(_check_password)])
+async def auth_test():
+    return {"status": "ok"}
+
+
+@app.post("/recipes/generate", response_model=RecipeResponse, dependencies=[Depends(_check_password)])
+async def generate_recipes(request: RecipeRequest):
+    user_message = _build_user_message(request)
+
+    for attempt in range(3):
+        try:
+            stream = await _client.chat.completions.create(
+                model=settings.nvidia_model,
+                messages=[
+                    {"role": "system", "content": SYSTEM_PROMPT},
+                    {"role": "user", "content": user_message},
+                ],
+                temperature=settings.nvidia_temperature,
+                top_p=settings.nvidia_top_p,
+                max_tokens=settings.nvidia_max_tokens,
+                extra_body={
+                    "chat_template_kwargs": {"enable_thinking": True},
+                    "reasoning_budget": settings.nvidia_reasoning_budget,
+                },
+                stream=True,
+            )
+            content = ""
+            async for chunk in stream:
+                if not chunk.choices:
+                    continue
+                delta = chunk.choices[0].delta
+                if delta.content is not None:
+                    content += delta.content
+
+            data = json.loads(content.strip())
+            return RecipeResponse(**data)
+        except json.JSONDecodeError:
+            if attempt == 2:
+                raise HTTPException(status_code=502, detail="Il modello non ha prodotto JSON valido dopo 3 tentativi")
+            logger.warning("Tentativo %d: JSON non valido, retry...", attempt + 1)
+        except Exception as e:
+            raise HTTPException(status_code=502, detail=str(e))
+
+
+def _build_user_message(request: RecipeRequest) -> str:
+    ingredients_str = "\n".join(
+        f"- {ing.name}: {ing.quantity} {ing.unit}" for ing in request.ingredients
+    )
+    p = request.preferences
+    return (
+        f"Ingredienti disponibili:\n{ingredients_str}\n\n"
+        f"Preferenze:\n"
+        f"- Porzioni: {p.servings}\n"
+        f"- Tempo massimo: {p.maxTimeMinutes} minuti\n"
+        f"- Difficoltà: {p.difficulty}\n"
+        f"- Dieta: {p.diet}\n"
+        f"- Allergie: {', '.join(p.allergies) or 'nessuna'}\n"
+        f"- Alimenti da evitare: {', '.join(p.avoid) or 'nessuno'}\n"
+        f"- Strumenti disponibili: {', '.join(p.tools) or 'standard'}\n\n"
+        "Genera 3 ricette in JSON."
+    )