Durable Task Scheduler: add docs related to new client-side integration package

[philliphoff]

Aspire PR#15928 adds client-side integration for Durable Task Scheduler that will need corresponding docs.

[IEvangelist]

Triage → @Copilot

Upstream: microsoft/aspire#15928 — adds a new client-side integration package for Durable Task Scheduler (DTS).

Scope: Document the new client-side integration. Locate the existing DTS docs under src/frontend/src/content/docs/integrations/cloud/azure/ (host-side); add or extend the page that covers the client-side package, mirroring the structure of other "client integration" pages (e.g. SQL Server / Cosmos client integrations).

Acceptance

• Confirm package id, options class, and the AddX(...) extension methods by reading the merged PR diff.
• Cover: AddDurableTaskScheduler(...) (or whatever the public surface is), configuration sections, telemetry/health checks if present, and a minimal end-to-end snippet (AppHost + client Program.cs).
• Cross-link from the existing host-side DTS page.
• No unrelated edits.

If #214 (Azure Functions + DTS examples) overlaps with this, fold the client wiring example into both pages with the same code snippet rather than duplicating.