chore(lint): unify formatting on golangci-lint fmt (gofumpt), uncap issue reporting, fix gofumpt drift

- make format 现在与 code-check 使用同一格式化器（golangci-lint fmt），消除 goimports -local 与 gofumpt 的格式拉锯
- .golangci.yml 关闭默认 50/3 截断，完整上报所有问题（只增强不弱化）
- 全库 gofumpt 规范化（203 files, 纯格式无行为变更）

backend/plugins/infra/storage/objectstore/db_helper.go

@@ -4,13 +4,12 @@
 package objectstore
 
 import (
+	"Wavelet/core"
+	"Wavelet/core/contracts"
 	"context"
 	"sync"
 
 	"gorm.io/gorm"
-
-	"Wavelet/core"
-	"Wavelet/core/contracts"
 )
 
 var (

backend/plugins/infra/storage/objectstore/http.go

@@ -4,13 +4,12 @@
 package objectstore
 
 import (
+	"Wavelet/pkg/httppool"
 	"context"
 	"fmt"
 	"net/http"
 	"net/url"
 	"time"
-
-	"Wavelet/pkg/httppool"
 )
 
 func getHTTPObject(ctx context.Context, baseURL, key string) (*Object, error) {

backend/plugins/infra/storage/objectstore/webdav.go

@@ -4,6 +4,7 @@
 package objectstore
 
 import (
+	"Wavelet/pkg/httppool"
 	"context"
 	"fmt"
 	"io"
@@ -12,8 +13,6 @@ import (
 	"strings"
 
 	"github.com/studio-b12/gowebdav"
-
-	"Wavelet/pkg/httppool"
 )
 
 type contextTransport struct {