feat: DeepSeek V4 Flash primario, Big Pickle fallback

- deepseek-v4-flash su opencode/go come modello primario
- big-pickle su opencode/zen come fallback (gratuito)
- Fallback automatico su censura "User Safety" o errore HTTP
- Aggiornati .env, config.py, start.sh, docker-compose.yml

src/engine/providers.py

@@ -84,13 +84,15 @@ class OpenRouterProvider(LLMProvider):
 
 
 class LocalProvider(LLMProvider):
-    def __init__(self, base_url: str, model: str, api_key: str = "", timeout: int = 60):
+    def __init__(self, base_url: str, model: str, api_key: str = "",
+                 timeout: int = 60, fallbacks: list[tuple[str, str]] | None = None):
         self.base_url = base_url.rstrip("/")
         self.model = model
         self.api_key = api_key
         self.timeout = timeout
+        self.fallbacks = fallbacks or []
 
-    def ask(self, prompt: str, system: str = "") -> str:
+    def _call(self, base_url: str, model: str, prompt: str, system: str) -> str:
         messages = []
         if system:
             messages.append({"role": "system", "content": system})
@@ -100,10 +102,10 @@ class LocalProvider(LLMProvider):
         if self.api_key:
             headers["Authorization"] = f"Bearer {self.api_key}"
 
-        body = {"model": self.model, "messages": messages, "stream": False}
+        body = {"model": model, "messages": messages, "stream": False}
 
         resp = httpx.post(
-            f"{self.base_url}/chat/completions",
+            f"{base_url}/chat/completions",
             json=body,
             headers=headers,
             timeout=self.timeout,
@@ -112,6 +114,21 @@ class LocalProvider(LLMProvider):
         data = resp.json()
         return data["choices"][0]["message"]["content"]
 
+    def ask(self, prompt: str, system: str = "") -> str:
+        candidates = [(self.base_url, self.model)] + self.fallbacks
+        last_err = None
+        for base_url, model in candidates:
+            try:
+                text = self._call(base_url, model, prompt, system)
+                # Rileva risposte di censura del modello gratuito
+                if "User Safety" in text and "safe" in text.lower():
+                    raise ValueError(f"Modello '{model}' ha censurato la risposta: {text[:60]}")
+                return text
+            except Exception as e:
+                last_err = e
+                continue
+        raise last_err  # type: ignore
+
 
 _registry: dict[str, Any] = {
     "ollama": OllamaProvider,
@@ -136,6 +153,9 @@ def create_provider(cfg: ProviderConfig | None = None) -> LLMProvider:
             raise ValueError("DCC_OPENROUTER_KEY non configurata")
         return cls(key, cfg.openrouter_model, cfg.timeout, cfg.openrouter_free_fallback)
     elif cfg.kind == "local":
-        return cls(cfg.local_base_url, cfg.local_model, cfg.local_api_key, cfg.timeout)
+        fallbacks = []
+        if cfg.local_fallback_url and cfg.local_fallback_model:
+            fallbacks.append((cfg.local_fallback_url, cfg.local_fallback_model))
+        return cls(cfg.local_base_url, cfg.local_model, cfg.local_api_key, cfg.timeout, fallbacks=fallbacks)
     else:
         raise ValueError(f"Provider non implementato: {cfg.kind}")