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/domain/upload/storage/access_state.go

@@ -5,12 +5,11 @@
 package storage
 
 import (
+	"Wavelet/core/contracts"
+	"Wavelet/plugins/domain/upload/shared"
 	"context"
 	"sync"
 	"time"
-
-	"Wavelet/core/contracts"
-	"Wavelet/plugins/domain/upload/shared"
 )
 
 // MigrationAccessState captures cached migration maintenance state.

backend/plugins/domain/upload/storage/migration.go

@@ -4,6 +4,8 @@
 package storage
 
 import (
+	"Wavelet/core/contracts"
+	"Wavelet/plugins/domain/upload/shared"
 	"context"
 	"encoding/json"
 	"errors"
@@ -11,9 +13,6 @@ import (
 	"strings"
 
 	"gorm.io/gorm"
-
-	"Wavelet/core/contracts"
-	"Wavelet/plugins/domain/upload/shared"
 )
 
 // StorageMigrationTask is the task name for storage migration.

backend/plugins/domain/upload/storage/storage_ops.go

@@ -4,13 +4,12 @@
 package storage
 
 import (
-	"context"
-	"errors"
-
 	"Wavelet/core/contracts"
 	"Wavelet/pkg/logger"
 	"Wavelet/plugins/domain/upload/models"
 	"Wavelet/plugins/domain/upload/shared"
+	"context"
+	"errors"
 )
 
 // ReadOnly checks if the storage system is in read-only maintenance mode.