Feature request: Support for New Name.com API (v4 Deprecated from 2026)

Problem Description:
Name.com officially announced that starting 2026, their current v4 API for DNS management will be deprecated and shut down. The new API (core/v1) has different endpoints, authentication, and response formats.

Expected Behavior:
acme.sh should update its dns_namecom.sh DNS API plugin to support the new Name.com core/v1 API so users can continue issuing and renewing certificates without interruption.

Current Behavior:
The current dns_namecom.sh plugin relies on the deprecated v4 API endpoints which will become unusable starting from 2026, causing certificate issuance/renewal failures for users using Name.com DNS validation.

Suggested Solution:
Refactor the Name.com DNS API plugin in acme.sh to:

Use the new https://api.name.com/core/v1/ endpoints

Update authentication handling if necessary

Adapt to the new JSON request/response formats

References:

Name.com API deprecation announcement: https://docs.name.com/changelog/changelog

The issue points to the `dns_namecom.sh` plugin; open that file first and inspect how it currently builds v4 endpoint URLs, handles authentication, and parses JSON responses. Replace those request/response paths with Name.com `core/v1` equivalents and adjust payload/field handling accordingly. Then run a Name.com DNS challenge flow (TXT add/remove plus issue/renew) to confirm behavior still works and deprecated v4 endpoints are no longer used.

索引モデルが issue の本文から書いたものです。