Add IM User business list method

[mesilov]

Problem

The live Bitrix24 im scope exposes im.user.business.list, but the SDK IM User service currently implements only:

• im.user.get
• im.user.list.get

The missing method belongs in the existing Bitrix24\SDK\Services\IM\User\Service\User service area unless live response verification shows that it needs a separate service/result boundary. It is also listed in the umbrella IM scope tracking issue #422.

Documentation

• im.user.business.list — no official public apidocs.bitrix24.com method page was found via the Bitrix24 documentation MCP or direct apidocs search.
• Scope overview: https://apidocs.bitrix24.com/api-reference/chats/index.html

Proposed solution

Add SDK support for im.user.business.list in the IM User service area:

• Verify the live parameter contract and response shape against the Bitrix24 playground.
• Add a typed SDK service method with ApiEndpointMetadata for im.user.business.list.
• Add or reuse result wrappers based on the verified response shape.
• Add focused unit tests for request payload mapping and result type.
• Add integration coverage against the live Bitrix24 playground, or document any live-environment blocker in the task plan.

Acceptance criteria

• Factory::getServiceBuilder()->getIMScope()->user() exposes a SDK method for im.user.business.list.
• The implementation uses the exact live REST method name and keeps the im scope metadata.
• Unit tests cover payload mapping and result type.
• Integration tests cover the live response shape or document any live-environment blocker in the task plan.
• make sdk-coverage-v1-show no longer lists im.user.business.list as unsupported in the im scope.