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/plugin.go

@@ -5,15 +5,14 @@
 package storage
 
 import (
-	"context"
-	"errors"
-	"fmt"
-	"io"
-
 	"Wavelet/core"
 	"Wavelet/core/contracts"
 	"Wavelet/plugins/infra/storage/diskcache"
 	"Wavelet/plugins/infra/storage/objectstore"
+	"context"
+	"errors"
+	"fmt"
+	"io"
 )
 
 // Option configures the storage plugin.