feat: 配置 golangci-lint 静态分析并修复存量违规

- 新增 backend/.golangci.yml 配置 12 个 linter（forbidigo、errorlint、errcheck、staticcheck、revive、gocritic、gosec、bodyclose、noctx、nilerr、goimports、gocyclo）
- 新增 lefthook.yml 配置 pre-commit hook 自动运行 lint
- 修复存量代码违规：errors.Is/As 替换、zap.Error 替换、import 排序、errcheck 修复
- 更新 README 补充编码规范说明
- 归档 backend-code-lint 变更

backend/internal/service/stats_buffer.go

@@ -6,9 +6,10 @@ import (
 	"sync/atomic"
 	"time"
 
+	"nex/backend/internal/repository"
+
 	"go.uber.org/zap"
 
-	"nex/backend/internal/repository"
 	pkglogger "nex/backend/pkg/logger"
 )
 
@@ -67,13 +68,21 @@ func (b *StatsBuffer) Increment(providerID, modelName string) {
 
 	var counter *int64
 	if v, ok := b.counters.Load(key); ok {
-		counter = v.(*int64)
+		if existing, ok := v.(*int64); ok {
+			counter = existing
+		} else {
+			return
+		}
 	} else {
 		val := int64(0)
 		counter = &val
 		actual, loaded := b.counters.LoadOrStore(key, counter)
 		if loaded {
-			counter = actual.(*int64)
+			existing, ok := actual.(*int64)
+			if !ok {
+				return
+			}
+			counter = existing
 		}
 	}
 
@@ -117,13 +126,20 @@ func (b *StatsBuffer) flush() {
 
 	var entries []statEntry
 	b.counters.Range(func(key, value interface{}) bool {
-		keyStr := key.(string)
+		keyStr, ok := key.(string)
+		if !ok {
+			return true
+		}
+
 		parts := strings.Split(keyStr, "/")
 		if len(parts) != 3 {
 			return true
 		}
 
-		counter := value.(*int64)
+		counter, ok := value.(*int64)
+		if !ok {
+			return true
+		}
 		count := atomic.SwapInt64(counter, 0)
 
 		if count > 0 {
@@ -143,8 +159,17 @@ func (b *StatsBuffer) flush() {
 
 	success := 0
 	for _, entry := range entries {
-		date, _ := time.Parse("2006-01-02", entry.date)
-		err := b.statsRepo.BatchUpdate(entry.providerID, entry.modelName, date, int(entry.count))
+		date, err := time.Parse("2006-01-02", entry.date)
+		if err != nil {
+			b.logger.Error("解析统计日期失败",
+				zap.String("provider_id", entry.providerID),
+				zap.String("model_name", entry.modelName),
+				zap.String("date", entry.date),
+				zap.Error(err))
+			continue
+		}
+
+		err = b.statsRepo.BatchUpdate(entry.providerID, entry.modelName, date, int(entry.count))
 		if err != nil {
 			b.logger.Error("批量更新统计失败",
 				zap.String("provider_id", entry.providerID),
@@ -154,8 +179,10 @@ func (b *StatsBuffer) flush() {
 
 			key := entry.providerID + "/" + entry.modelName + "/" + entry.date
 			if v, ok := b.counters.Load(key); ok {
-				counter := v.(*int64)
-				atomic.AddInt64(counter, entry.count)
+				counter, ok := v.(*int64)
+				if ok {
+					atomic.AddInt64(counter, entry.count)
+				}
 			}
 		} else {
 			success++