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/geoip.go

@@ -1,7 +1,11 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
 // Package geoip resolves geographic information for IP addresses.
 package geoip
 
 import (
+	"errors"
 	"fmt"
 	"log/slog"
 	"net"
@@ -138,7 +142,7 @@ func InitGeoIP(provider string) {
 // GetGeoInfo looks up geographic information for ip using the active provider.
 func GetGeoInfo(ip net.IP) (*GeoInfo, error) {
 	if ip == nil {
-		return nil, fmt.Errorf("IP address cannot be nil")
+		return nil, errors.New("IP address cannot be nil")
 	}
 	provider := getProvider()
 	cacheKey := provider.Name() + ":" + ip.String()
@@ -157,7 +161,7 @@ func GetGeoInfo(ip net.IP) (*GeoInfo, error) {
 // LookupGeoInfoWithProvider looks up geographic information using a temporary provider.
 func LookupGeoInfoWithProvider(providerName string, ip net.IP) (*GeoInfo, error) {
 	if ip == nil {
-		return nil, fmt.Errorf("IP address cannot be nil")
+		return nil, errors.New("IP address cannot be nil")
 	}
 
 	provider, err := providerFactory(normalizeProvider(providerName))