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)

.gitignore

@@ -8,6 +8,8 @@ __pycache__/
 *.pyc
 *.pyo
 *.db
+*.db-shm
+*.db-wal
 
 # Tool configuration (not part of project)
 .opencode/