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/config_version/snapshot.go

@@ -8,6 +8,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -199,9 +200,7 @@ func buildCurrentConfigBundle(ctx context.Context, requireRoutes bool) (*configB
 		return nil, err
 	}
 
-	mainConfig := ""
-	routeConfig := ""
-	checksum := ""
+	var mainConfig, routeConfig, checksum string
 	supportFiles := []SupportFile(nil)
 
 	rendered, renderErr := renderSnapshotConfig(string(snapshotJSON), certificateFiles)
@@ -429,7 +428,7 @@ func buildSnapshotWAFIPGroups(ctx context.Context, idSet map[uint]struct{}) ([]s
 	for id := range idSet {
 		ids = append(ids, id)
 	}
-	sort.Slice(ids, func(i, j int) bool { return ids[i] < ids[j] })
+	slices.Sort(ids)
 	groups, err := listWAFIPGroupsByIDs(ctx, ids)
 	if err != nil {
 		return nil, err
@@ -477,7 +476,7 @@ func decodeIPList(raw string) ([]string, error) {
 	}
 	var items []string
 	if err := json.Unmarshal([]byte(text), &items); err != nil {
-		return nil, fmt.Errorf("ip_list payload is invalid")
+		return nil, errors.New("ip_list payload is invalid")
 	}
 	return items, nil
 }
@@ -629,7 +628,7 @@ func buildCertificateSupportFiles(ctx context.Context, routes []snapshotRoute) (
 	for certID := range certIDSet {
 		certIDs = append(certIDs, certID)
 	}
-	sort.Slice(certIDs, func(i, j int) bool { return certIDs[i] < certIDs[j] })
+	slices.Sort(certIDs)
 	files := make([]SupportFile, 0, len(certIDs)*supportFilesPerCertificate)
 	for _, certID := range certIDs {
 		certificate, err := repository.GetTLSCertificateByID(ctx, certID)