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/agent/sync/service.go

@@ -12,7 +12,7 @@ import (
 	"fmt"
 	"io"
 	"log/slog"
-	"sort"
+	"slices"
 	"strconv"
 	"strings"
 	"sync"
@@ -363,7 +363,7 @@ func referencedWAFIPGroupIDs(supportFiles []protocol.SupportFile) ([]uint, error
 	for id := range seen {
 		ids = append(ids, id)
 	}
-	sort.Slice(ids, func(i, j int) bool { return ids[i] < ids[j] })
+	slices.Sort(ids)
 	return ids, nil
 }
 
@@ -426,7 +426,7 @@ func (s *Service) ensureRuntimeForCurrentConfig(ctx context.Context, mode string
 				snapshot.OpenrestyMessage = "safe default fallback runtime started"
 				return nil
 			}
-			err = fmt.Errorf("%v; fallback recovery failed: %w", err, fallbackErr)
+			err = fmt.Errorf("%w; fallback recovery failed: %w", err, fallbackErr)
 		}
 		snapshot.OpenrestyStatus = protocol.OpenrestyStatusUnhealthy
 		snapshot.OpenrestyMessage = err.Error()