Clarify Power Platform service communications guidance

[Kara Cortez (karacortez)]

Summary

• clarify when administrators should use Message center, authenticated Service health, the Power Platform admin center, and the public Service Health Status page
• add direct links for configuring Message center and Service health email notifications
• update service communications API guidance to Microsoft Graph and explain custom dashboard, workflow, messaging, and SMS integrations
• consolidate duplicate maintenance guidance and refresh outdated service, mobile app, Planner, and released-version links
• improve incident definitions, reporting steps, update expectations, and general page clarity

Context

This addresses feedback requesting a clarity scrub, direct alert-setup links, a clear distinction between authenticated and public status sources, and actionable API/custom-integration guidance.

[learn-build-service-prod]

Learn Build status updates of commit de98d89:

✅ Validation status: passed

File	Status	Preview URL	Details
power-platform/admin/policies-communications.md	✅Succeeded

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