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)

.gitignore

@@ -18,6 +18,14 @@ __pycache__/
 # Generated graph artifacts
 graphify-out/
 
+# Virtual environments
+env/
+
+# Node.js artifacts (not used by this Python project)
+node_modules/
+package-lock.json
+package.json
+
 # OS files
 .DS_Store
 Thumbs.db