refactor: cleanup unused code and simplify internal packages

This commit performs a significant cleanup of the codebase by removing unused functions, methods, and entire files across various internal modules. This reduces technical debt and simplifies the project structure.

Key changes include:
- **cache**: Removed unused cache key generators and metrics snapshots.
- **dto**: Removed redundant converter functions and segment creation helpers.
- **middleware**: Deleted the unused `logger.go` middleware and simplified `ratelimit.go` and `casbin.go`.
- **model**: Removed unused ID helpers, database closing functions, and batch decryption logic.
- **pkg**: Cleaned up unused utility functions in `circuitbreaker`, `crypto`, `cursor`, `hook`, and `utils`.
- **service**: Deleted `account_cleanup_service.go` and removed unused helper functions in `log_cleanup_service.go` and `sensitive_service.go`.
- **repository**: Removed unused private loading methods in `comment_repo.go`.

internal/pkg/crypto/batch_decrypt.go

@@ -1,7 +1,6 @@
 package crypto
 
 import (
-	"encoding/json"
 	"sync"
 )
 
@@ -75,35 +74,3 @@ func (e *MessageEncryptor) BatchDecrypt(ciphertexts []string, workerCount int) [
 	return results
 }
 
-// DecryptMessageSegments 解密消息段 JSON
-// 这是一个便捷方法，直接返回解析后的 MessageSegments
-func (e *MessageEncryptor) DecryptMessageSegments(ciphertext string) ([]byte, error) {
-	if e == nil || ciphertext == "" {
-		return nil, nil
-	}
-	return e.Decrypt(ciphertext)
-}
-
-// TryParseMessageSegments 尝试解析消息段
-// 先尝试解密，如果失败则尝试直接解析（兼容未加密的旧数据）
-func TryParseMessageSegments(ciphertext string, segments any) error {
-	if ciphertext == "" {
-		return nil
-	}
-
-	encryptor := GetMessageEncryptor()
-	if encryptor == nil {
-		// 加密器未初始化，直接解析
-		return json.Unmarshal([]byte(ciphertext), segments)
-	}
-
-	// 尝试解密
-	plaintext, err := encryptor.Decrypt(ciphertext)
-	if err != nil {
-		// 解密失败，可能是未加密的旧数据，尝试直接解析
-		return json.Unmarshal([]byte(ciphertext), segments)
-	}
-
-	// 解析解密后的数据
-	return json.Unmarshal(plaintext, segments)
-}