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/cache/plugin.go

@@ -5,6 +5,10 @@
 package cache
 
 import (
+	"Wavelet/core"
+	"Wavelet/core/contracts"
+	"Wavelet/pkg/cache/ram"
+	"Wavelet/pkg/util"
 	"context"
 	"encoding/json"
 	"errors"
@@ -12,11 +16,6 @@ import (
 	"time"
 
 	"github.com/redis/go-redis/v9"
-
-	"Wavelet/core"
-	"Wavelet/core/contracts"
-	"Wavelet/pkg/cache/ram"
-	"Wavelet/pkg/util"
 )
 
 const (

backend/plugins/infra/cache/plugin_test.go

@@ -4,6 +4,9 @@
 package cache_test
 
 import (
+	"Wavelet/core"
+	"Wavelet/core/contracts"
+	"Wavelet/plugins/infra/cache"
 	"context"
 	"testing"
 	"time"
@@ -12,10 +15,6 @@ import (
 	"github.com/redis/go-redis/v9"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-
-	"Wavelet/core"
-	"Wavelet/core/contracts"
-	"Wavelet/plugins/infra/cache"
 )
 
 func TestCachePluginOperations(t *testing.T) {

backend/plugins/infra/cache/redis.go

@@ -4,6 +4,7 @@
 package cache
 
 import (
+	"Wavelet/pkg/config"
 	"context"
 	"encoding/json"
 	"fmt"
@@ -15,14 +16,10 @@ import (
 	"github.com/redis/go-redis/v9"
 	"github.com/redis/go-redis/v9/maintnotifications"
 	"go.opentelemetry.io/otel/attribute"
-
-	"Wavelet/pkg/config"
 )
 
-var (
-	// Redis 全局 Redis 客户端实例
-	Redis redis.UniversalClient
-)
+// Redis 全局 Redis 客户端实例
+var Redis redis.UniversalClient
 
 // InitRedis 初始化全局/默认 Redis 客户端实例
 func InitRedis() (redis.UniversalClient, error) {