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/config.py

@@ -0,0 +1,18 @@
+from pydantic_settings import BaseSettings
+
+
+class Settings(BaseSettings):
+    nvidia_api_key: str
+    app_password: str
+    nvidia_base_url: str = "https://integrate.api.nvidia.com/v1"
+    nvidia_model: str = "nvidia/nemotron-3-ultra-550b-a55b"
+    nvidia_timeout_seconds: int = 120
+    nvidia_max_tokens: int = 16384
+    nvidia_temperature: float = 1.0
+    nvidia_top_p: float = 0.95
+    nvidia_reasoning_budget: int = 2048
+
+    model_config = {"env_file": ".env"}
+
+
+settings = Settings()