refactor: introduce Wire dependency injection and interface-based architecture

- Add Google Wire for compile-time dependency injection
- Replace concrete service types with interfaces across handlers
- Remove global state (DB, cache) in favor of constructor injection
- Split monolithic files into focused modules:
  - config: separate files for each config domain
  - dto: converters split by domain (user, post, message, group)
  - cache: separate metrics.go and redis_cache.go
- Introduce unified apperrors package with string-based error codes
- Add transaction support with context-aware repository methods
- Upgrade golang.org/x/crypto from 0.17.0 to 0.26.0

internal/config/storage.go

@@ -0,0 +1,50 @@
+package config
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/minio/minio-go/v7"
+	"github.com/minio/minio-go/v7/pkg/credentials"
+)
+
+// S3Config S3 存储配置
+type S3Config struct {
+	Endpoint  string `mapstructure:"endpoint"`
+	AccessKey string `mapstructure:"access_key"`
+	SecretKey string `mapstructure:"secret_key"`
+	Bucket    string `mapstructure:"bucket"`
+	UseSSL    bool   `mapstructure:"use_ssl"`
+	Region    string `mapstructure:"region"`
+	Domain    string `mapstructure:"domain"` // 自定义域名，如 s3.carrot.skin
+}
+
+// NewS3 创建 S3 客户端
+func NewS3(cfg *S3Config) (*minio.Client, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
+	defer cancel()
+
+	client, err := minio.New(cfg.Endpoint, &minio.Options{
+		Creds:  credentials.NewStaticV4(cfg.AccessKey, cfg.SecretKey, ""),
+		Secure: cfg.UseSSL,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("failed to create S3 client: %w", err)
+	}
+
+	exists, err := client.BucketExists(ctx, cfg.Bucket)
+	if err != nil {
+		return nil, fmt.Errorf("failed to check bucket: %w", err)
+	}
+
+	if !exists {
+		if err := client.MakeBucket(ctx, cfg.Bucket, minio.MakeBucketOptions{
+			Region: cfg.Region,
+		}); err != nil {
+			return nil, fmt.Errorf("failed to create bucket: %w", err)
+		}
+	}
+
+	return client, nil
+}