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/util/format.go

@@ -1,3 +1,6 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
 // Package util provides shared formatting and string helper functions.
 package util
 
@@ -22,20 +25,20 @@ const (
 
 // Bytes2Size converts a byte count to a human-readable string with unit (B, KB, MB, GB).
 func Bytes2Size(num int64) string {
-	numStr := ""
+	var numStr string
 	unit := "B"
 	switch {
 	case num/int64(sizeGB) >= 1:
 		numStr = fmt.Sprintf("%.2f", float64(num)/float64(sizeGB))
 		unit = "GB"
 	case num/int64(sizeMB) >= 1:
-		numStr = fmt.Sprintf("%d", int(float64(num)/float64(sizeMB)))
+		numStr = strconv.Itoa(int(float64(num) / float64(sizeMB)))
 		unit = "MB"
 	case num/int64(sizeKB) >= 1:
-		numStr = fmt.Sprintf("%d", int(float64(num)/float64(sizeKB)))
+		numStr = strconv.Itoa(int(float64(num) / float64(sizeKB)))
 		unit = "KB"
 	default:
-		numStr = fmt.Sprintf("%d", num)
+		numStr = strconv.FormatInt(num, 10)
 	}
 	return numStr + " " + unit
 }