fix(observabilidade): close DB no SIGTERM e distinguir ENOENT/parse errors

api/server.ts

@@ -140,6 +140,16 @@ app.use('/api/operations', operationsRouter)
 const sessionsDb = openSessionsDb(process.env.OBSERVABILIDADE_DB ?? DEFAULT_DB_PATH)
 app.use('/api/sessions', createSessionsRouter(sessionsDb))
 
+function closeSessionsDb(): void {
+  try {
+    sessionsDb.close()
+  } catch (err) {
+    console.error('[sessionsDb] erro ao fechar:', err)
+  }
+}
+process.on('SIGTERM', closeSessionsDb)
+process.on('SIGINT', closeSessionsDb)
+
 // Serve static files in production
 if (isProduction) {
   // __dirname is /app/api/dist, need to go up 2 levels to /app/dist