8cf4e30a61
Replaced unrestricted locale component swapping with DuckDuckGo's documented kl allowlist and explicit aliases for provider-specific codes such as jp-jp, kr-kr, tw-tzh, and uk-en. Unsupported locale combinations now fall back to the existing us-en default instead of sending invalid kl values. Expanded regression coverage for Japanese, Korean, Traditional Chinese, and unsupported region-language combinations. Fixes #7110