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_writer.go

@@ -5,6 +5,7 @@ package analytics
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"strings"
 	"time"
@@ -30,7 +31,7 @@ func BatchInsertNodeMetricSnapshots(ctx context.Context, snapshots []analyticsmo
 		return nil
 	}
 	if db.ChConn == nil {
-		return fmt.Errorf("clickhouse connection is not initialized")
+		return errors.New("clickhouse connection is not initialized")
 	}
 
 	batch, err := db.ChConn.PrepareBatch(ctx, analyticsmodel.NodeMetricSnapshot{}.BatchInsertSQL())
@@ -102,7 +103,7 @@ func BatchInsertNodeEdgeHealth(ctx context.Context, rows []analyticsmodel.NodeEd
 		return nil
 	}
 	if db.ChConn == nil {
-		return fmt.Errorf("clickhouse connection is not initialized")
+		return errors.New("clickhouse connection is not initialized")
 	}
 	batch, err := db.ChConn.PrepareBatch(ctx, analyticsmodel.NodeEdgeHealth{}.BatchInsertSQL())
 	if err != nil {
@@ -160,7 +161,7 @@ func BatchInsertNodeObsFrps(ctx context.Context, observations []analyticsmodel.N
 		return nil
 	}
 	if db.ChConn == nil {
-		return fmt.Errorf("clickhouse connection is not initialized")
+		return errors.New("clickhouse connection is not initialized")
 	}
 
 	batch, err := db.ChConn.PrepareBatch(ctx, analyticsmodel.NodeObsFrps{}.BatchInsertSQL())
@@ -223,7 +224,7 @@ func BatchInsertNodeObsFrpc(ctx context.Context, observations []analyticsmodel.N
 		return nil
 	}
 	if db.ChConn == nil {
-		return fmt.Errorf("clickhouse connection is not initialized")
+		return errors.New("clickhouse connection is not initialized")
 	}
 
 	batch, err := db.ChConn.PrepareBatch(ctx, analyticsmodel.NodeObsFrpc{}.BatchInsertSQL())