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/model/id_helper.go

@@ -4,7 +4,6 @@ import (
 	"strconv"
 
 	"github.com/google/uuid"
-	"gorm.io/gorm"
 
 	"with_you/internal/pkg/utils"
 )
@@ -37,20 +36,3 @@ func SetSnowflakeInt64ID(id *int64) error {
 	return nil
 }
 
-func GenerateUUID() string {
-	return uuid.New().String()
-}
-
-func GenerateSnowflakeString() (string, error) {
-	id, err := utils.GetSnowflake().GenerateID()
-	if err != nil {
-		return "", err
-	}
-	return strconv.FormatInt(id, 10), nil
-}
-
-func GenerateSnowflakeInt64() (int64, error) {
-	return utils.GetSnowflake().GenerateID()
-}
-
-func nop(_ *gorm.DB) error { return nil }