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/infra/objectstore/local.go

@@ -5,6 +5,7 @@ package objectstore
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"mime"
@@ -20,7 +21,7 @@ type localBackend struct {
 func newLocalBackend(cfg LocalConfig) (*localBackend, error) {
 	root := filepath.Clean(cfg.Root)
 	if root == "" {
-		return nil, fmt.Errorf("local root is required")
+		return nil, errors.New("local root is required")
 	}
 	return &localBackend{root: root}, nil
 }
@@ -103,7 +104,7 @@ func (b *localBackend) path(key string) (string, error) {
 		}
 		rel, err := filepath.Rel(absRoot, absPath)
 		if err != nil || strings.HasPrefix(rel, "..") {
-			return "", fmt.Errorf("storage key escapes local root")
+			return "", errors.New("storage key escapes local root")
 		}
 		return cleanPath, nil
 	}
@@ -114,7 +115,7 @@ func (b *localBackend) path(key string) (string, error) {
 	path := filepath.Join(b.root, cleanKey)
 	rel, err := filepath.Rel(b.root, path)
 	if err != nil || strings.HasPrefix(rel, "..") {
-		return "", fmt.Errorf("storage key escapes local root")
+		return "", errors.New("storage key escapes local root")
 	}
 	return path, nil
 }