对接日志默认仅记录告警与错误

新增 LOG_INTEGRATION_LEVEL（默认 warn），压低 integration-*.log 体积；
失败类文案自动提升为 error，避免异常被过滤。

apps/backend/src/config/env-overrides.ts

@@ -33,6 +33,7 @@ export const ENV_OVERRIDES: readonly EnvOverride[] = [
   integerEnv("PORT", ["server", "port"]),
   stringEnv("DATA_ROOT", ["data", "root"], path.resolve),
   stringEnv("LOG_LEVEL", ["logging", "level"]),
+  stringEnv("LOG_INTEGRATION_LEVEL", ["logging", "integrationLevel"]),
   integerEnv("LOG_RETENTION_DAYS", ["logging", "retentionDays"]),
   stringEnv("DATABASE_URL", ["database", "url"]),
   booleanEnv("DATABASE_SSL", ["database", "ssl"]),