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/dto/report.go

@@ -108,11 +108,6 @@ type AdminBatchHandleResponse struct {
 
 // ==================== 转换函数 ====================
 
-func baseAdminReportFields(report *model.Report) (string, string) {
-	reason := string(report.Reason)
-	status := string(report.Status)
-	return reason, status
-}
 
 // ConvertReportToResponse 将 Report 模型转换为响应
 func ConvertReportToResponse(report *model.Report) *ReportResponse {