feat: AI Dungeon Master engine + web frontend

- Engine: stato SQLite, state machine, 10 approved tools, parser azioni
- LLM: multi-provider (Ollama/OpenRouter/Local), system prompt DCC
- DM cycle: LLM decide tool → engine esegue → narrazione + meccanica
- Dati avventura: JSON machine-readable con 9 aree, mostri, enigmi, quest
- Web: FastAPI + WebSocket backend, SPA frontend dark fantasy
- Ref: architecture-patterns/neon-scratch-lounge (separazione reasoning/execution)

src/engine/config.py

@@ -0,0 +1,35 @@
+from __future__ import annotations
+
+import os
+from dataclasses import dataclass
+from typing import Literal
+
+ProviderKind = Literal["ollama", "openrouter", "local"]
+
+@dataclass
+class ProviderConfig:
+    kind: ProviderKind = "openrouter"
+    ollama_base_url: str = "http://192.168.0.50:11434"
+    ollama_model: str = "gemma2:9b"
+    openrouter_api_key: str = ""
+    openrouter_model: str = "openrouter/free"
+    openrouter_free_fallback: bool = True
+    local_base_url: str = "http://192.168.0.240/v1"
+    local_api_key: str = ""
+    local_model: str = "big-pickle"
+    timeout: int = 60
+
+
+def load_from_env() -> ProviderConfig:
+    return ProviderConfig(
+        kind=os.getenv("DCC_LLM_PROVIDER", "openrouter"),  # type: ignore
+        ollama_base_url=os.getenv("DCC_OLLAMA_URL", "http://192.168.0.50:11434"),
+        ollama_model=os.getenv("DCC_OLLAMA_MODEL", "gemma2:9b"),
+        openrouter_api_key=os.getenv("OPENROUTER_API_KEY", ""),
+        openrouter_model=os.getenv("DCC_OPENROUTER_MODEL", "openrouter/free"),
+        openrouter_free_fallback=os.getenv("DCC_OR_FREE_FALLBACK", "1") == "1",
+        local_base_url=os.getenv("DCC_LOCAL_URL", "http://192.168.0.240/v1"),
+        local_api_key=os.getenv("DCC_LOCAL_KEY", ""),
+        local_model=os.getenv("DCC_LOCAL_MODEL", "big-pickle"),
+        timeout=int(os.getenv("DCC_LLM_TIMEOUT", "60")),
+    )