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/apps/upload/filesrv/file_server.go

@@ -68,7 +68,8 @@ func ServeFileByID(c *gin.Context) {
 			response.AbortNotFound(c, "文件记录未找到")
 			return
 		}
-		if _, ok := err.(*strconv.NumError); ok {
+		var numErr *strconv.NumError
+		if errors.As(err, &numErr) {
 			response.AbortBadRequest(c, "无效的上传ID")
 			return
 		}
@@ -133,6 +134,8 @@ func ServeUpload(c *gin.Context, upload *model.Upload) {
 			return
 		}
 		fallthrough
+	case fileTypeVideo, fileTypeAudio, fileTypeOther:
+		serveOriginalWithConditionalCheck(c, upload)
 	default:
 		serveOriginalWithConditionalCheck(c, upload)
 	}
@@ -205,7 +208,10 @@ func EnsureCompressedImageCache(
 		return nil, false, err
 	}
 
-	res := result.(compressedImageCacheResult)
+	res, ok := result.(compressedImageCacheResult)
+	if !ok {
+		return nil, false, fmt.Errorf("image compression flight returned unexpected type %T", result)
+	}
 	return res.bytes, res.cached, res.err
 }
 

internal/apps/upload/filesrv/file_server_test.go

@@ -357,6 +357,7 @@ func TestNormalizeImageQuality(t *testing.T) {
 }
 
 func configureLocalStorageRoot(t *testing.T, dbConn *gorm.DB, tempDir string) {
+	t.Helper()
 	var sc model.SystemConfig
 	if err := dbConn.Where("key = ?", model.ConfigKeyStorageConfig).First(&sc).Error; err != nil {
 		t.Fatalf("failed to find storage config: %v", err)