refactor: remediation plan Fase 0-4 completata

- Fase 0: env var allineate, SYSTEM_PROMPT deduplicato, .gitignore pulito
- Fase 1: GameContext isolato, ciclo DM unificato, provider thread-safe (contextvars)
- Fase 2: DB schema esteso (current_area_id, combat_state, character_items)
- Fase 3: thread-local connection pool + WAL + busy_timeout
- Fase 4: test suite (32 test, 100% pass)
- heuristic_fallback come parser di riserva (non secondo pilota)

src/engine/providers.py

@@ -131,9 +131,9 @@ def create_provider(cfg: ProviderConfig | None = None) -> LLMProvider:
     if cfg.kind == "ollama":
         return cls(cfg.ollama_base_url, cfg.ollama_model, cfg.timeout)
     elif cfg.kind == "openrouter":
-        key = cfg.openrouter_api_key or os.getenv("OPENROUTER_API_KEY", "")
+        key = cfg.openrouter_api_key or os.getenv("DCC_OPENROUTER_KEY", os.getenv("OPENROUTER_API_KEY", ""))
         if not key:
-            raise ValueError("OPENROUTER_API_KEY non configurata")
+            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)