DELETE /api/scaling-groups/{name} fails with non-ASCII characters in group name

## Problem Description

The DELETE endpoint for scaling groups (`/api/scaling-groups/{name`}) may fail when the scaling group name contains non-ASCII characters (e.g., Korean characters).

## Expected Behavior

The endpoint should properly handle scaling group names with non-ASCII characters, including Korean, and successfully delete the scaling group.

## Current Behavior

The endpoint may fail to properly process requests when the scaling group name in the URL path contains non-ASCII characters due to URL encoding issues.

## Steps to Reproduce

1. Create a scaling group with a Korean name (e.g., "테스트그룹")
1. Attempt to delete it using DELETE /api/scaling-groups/테스트그룹
1. Observe the failure

## Acceptance Criteria

- Verify the issue exists with Korean and other non-ASCII characters
- Fix URL encoding/decoding to properly handle non-ASCII characters
- Ensure the endpoint works correctly with both ASCII and non-ASCII group names
- Add tests to prevent regression

JIRA Issue: BA-2574