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/repository/analytics/node_observability.go

@@ -5,8 +5,9 @@ package analytics
 
 import (
 	"context"
+	"errors"
 	"fmt"
-	"sort"
+	"slices"
 	"time"
 
 	"github.com/ClickHouse/clickhouse-go/v2/lib/driver"
@@ -16,7 +17,7 @@ import (
 
 func observabilityConn() (driver.Conn, error) {
 	if db.ChConn == nil {
-		return nil, fmt.Errorf("clickhouse connection is not initialized")
+		return nil, errors.New("clickhouse connection is not initialized")
 	}
 	return db.ChConn, nil
 }
@@ -367,7 +368,7 @@ func mergeNodeMetricHourlyPreferRollup(rollup, raw []NodeMetricHourly) []NodeMet
 	}
 	result := make([]NodeMetricHourly, 0, len(order))
 	// Keep chronological order of first-seen keys; re-sort by hour for stability.
-	sort.Slice(order, func(i, j int) bool { return order[i] < order[j] })
+	slices.Sort(order)
 	for _, key := range order {
 		result = append(result, byHour[key])
 	}