后端与全仓代码质量清理（golangci 扩展集 · 测试质量 · 并发安全 · 文档同步）

代码质量全量清理，零行为变化：golangci 扩展集 13 类 linter（gosec/modernize/perfsprint/canonicalheader/usestdlibvars/wastedassign/intrange/errorlint/forcetypeassert/recvcheck/exhaustive/unparam）全量修复，测试代码质量（testifylint/thelper/usetesting）25→0，frpc 进程生命周期真 bug（进程组击杀）、全仓 go test -race 6 类数据竞争（含 1 个生产竞争）、SPDX license 头补齐 131 文件、前端测试套件 next-intl 迁移后 44 失败→全绿、过期 swagger 文档重新生成、pnpm-workspace 构建审批。

Experiments: #2-#17, #18, #20, #21, #23
Metric: total_issues 108 → 8 (-92.6%)

pkg/geoip/emptyProvider.go

@@ -1,7 +1,10 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
 package geoip
 
 import (
-	"fmt"
+	"errors"
 	"net"
 )
 
@@ -20,12 +23,12 @@ func (e *EmptyProvider) Initialize() error {
 
 // GetGeoInfo reports that no GeoIP provider has been configured.
 func (e *EmptyProvider) GetGeoInfo(_ net.IP) (*GeoInfo, error) {
-	return nil, fmt.Errorf("you are using an empty GeoIP provider, please set a valid provider")
+	return nil, errors.New("you are using an empty GeoIP provider, please set a valid provider")
 }
 
 // UpdateDatabase reports that no GeoIP provider has been configured.
 func (e *EmptyProvider) UpdateDatabase() error {
-	return fmt.Errorf("you are using an empty GeoIP provider, please set a valid provider")
+	return errors.New("you are using an empty GeoIP provider, please set a valid provider")
 }
 
 // Close releases resources held by the empty provider.