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%)

internal/apps/openflare/agent/observability.go

@@ -179,18 +179,9 @@ func buildNodeAccessLogRecords(nodeID string, direct []NodeAccessLog, buffered [
 	records := make([]*model.OpenFlareAccessLog, 0, total)
 	appendLogs := func(logs []NodeAccessLog) {
 		for _, item := range logs {
-			bytesSent := item.BytesSent
-			if bytesSent < 0 {
-				bytesSent = 0
-			}
-			requestLength := item.RequestLength
-			if requestLength < 0 {
-				requestLength = 0
-			}
-			requestTimeMs := item.RequestTimeMs
-			if requestTimeMs < 0 {
-				requestTimeMs = 0
-			}
+			bytesSent := max(item.BytesSent, 0)
+			requestLength := max(item.RequestLength, 0)
+			requestTimeMs := max(item.RequestTimeMs, 0)
 			record := &model.OpenFlareAccessLog{
 				NodeID:        nodeID,
 				LoggedAt:      timeFromUnix(item.LoggedAtUnix, reportedAt),