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/waf/ip_group_sync.go

@@ -11,6 +11,7 @@ import (
 	"fmt"
 	"io"
 	"log/slog"
+	"maps"
 	"net"
 	"net/http"
 	"net/netip"
@@ -325,9 +326,7 @@ func evaluateParsedIPGroupAutoConfig(ctx context.Context, config ipGroupAutoConf
 			lastSeen = time.Unix(item.LastSeenEpoch, 0).UTC()
 		}
 		statusCounts := make(map[int]int, len(item.StatusCounts))
-		for code, count := range item.StatusCounts {
-			statusCounts[code] = count
-		}
+		maps.Copy(statusCounts, item.StatusCounts)
 		accumulators[ip] = &ipGroupAutoAccumulator{
 			ip:               ip,
 			requestCount:     item.RequestCount,
@@ -404,7 +403,7 @@ func downloadIPGroupSubscription(ctx context.Context, rawURL string) ([]byte, er
 		return nil, err
 	}
 	client := http.Client{Timeout: 15 * time.Second}
-	req, err := http.NewRequestWithContext(ctx, "GET", rawURL, nil)
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, rawURL, nil)
 	if err != nil {
 		return nil, fmt.Errorf("下载订阅失败: %w", err)
 	}
@@ -479,7 +478,7 @@ func selectJSONMappingNodes(payload any, mappingRule string) ([]any, error) {
 	}
 	rule = strings.TrimPrefix(rule, "$.")
 	nodes := []any{payload}
-	for _, rawSegment := range strings.Split(rule, ".") {
+	for rawSegment := range strings.SplitSeq(rule, ".") {
 		segment := strings.TrimSpace(rawSegment)
 		if segment == "" {
 			continue