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/handler/provider_handler.go

@@ -4,13 +4,13 @@ import (
 	"errors"
 	"net/http"
 
+	"nex/backend/internal/domain"
+	"nex/backend/internal/service"
+
 	"github.com/gin-gonic/gin"
 	"gorm.io/gorm"
 
 	appErrors "nex/backend/pkg/errors"
-
-	"nex/backend/internal/domain"
-	"nex/backend/internal/service"
 )
 
 // ProviderHandler 供应商管理处理器
@@ -55,7 +55,7 @@ func (h *ProviderHandler) CreateProvider(c *gin.Context) {
 
 	err := h.providerService.Create(provider)
 	if err != nil {
-		if err == appErrors.ErrInvalidProviderID {
+		if errors.Is(err, appErrors.ErrInvalidProviderID) {
 			c.JSON(http.StatusBadRequest, gin.H{
 				"error": appErrors.ErrInvalidProviderID.Message,
 				"code":  appErrors.ErrInvalidProviderID.Code,
@@ -86,7 +86,7 @@ func (h *ProviderHandler) GetProvider(c *gin.Context) {
 
 	provider, err := h.providerService.Get(id)
 	if err != nil {
-		if err == gorm.ErrRecordNotFound {
+		if errors.Is(err, gorm.ErrRecordNotFound) {
 			c.JSON(http.StatusNotFound, gin.H{
 				"error": "供应商未找到",
 			})
@@ -113,7 +113,7 @@ func (h *ProviderHandler) UpdateProvider(c *gin.Context) {
 
 	err := h.providerService.Update(id, req)
 	if err != nil {
-		if err == gorm.ErrRecordNotFound {
+		if errors.Is(err, gorm.ErrRecordNotFound) {
 			c.JSON(http.StatusNotFound, gin.H{
 				"error": "供应商未找到",
 			})
@@ -145,7 +145,7 @@ func (h *ProviderHandler) DeleteProvider(c *gin.Context) {
 
 	err := h.providerService.Delete(id)
 	if err != nil {
-		if err == gorm.ErrRecordNotFound {
+		if errors.Is(err, gorm.ErrRecordNotFound) {
 			c.JSON(http.StatusNotFound, gin.H{
 				"error": "供应商未找到",
 			})