docs: simplify the customer setup walkthrough

[Hou (SciencePotato)]

Summary

Make customer onboarding easier to follow, with five illustrated steps: get ready, register the application, run guided setup, connect and test the provider, then activate and hand over.

• Keep the main guide provider-neutral, with exact credentials and technical settings in linked references.
• Improve navigation across setup, validation, monitoring, troubleshooting, and optional developer guides.
• Preserve permissions, billing, authentication, assisted testing/activation, renewal, and rollback safeguards.
• Add redacted portal views and real script input captures. Explain how to review the plan without approving deployment.

Documentation and images only; no runtime or infrastructure code changes.

Illustrations and their limits

The 12 screenshots cover app registration and IDs, script inputs and choices, an existing resource group, Function authentication, monitoring navigation and a Logs query, sample Security Store offers, and Key Vault credential entry. Identifying details are cropped or permanently covered in the image pixels. Named provider examples stay in the detailed onboarding guide, not the main README.

The original script capture used source 48b94a3d42e74ef2a1a65a286a7f8e24a53353ff. It collected inputs but stopped at prerequisite checks because the required Microsoft Graph context was not established. The approval prompt was not reached. A dedicated application registration was created, but no Azure hosting resources were deployed, no authentication policy was activated, and no provider messages were sent during that walkthrough.

Other portal views show an existing nonproduction deployment. The registration-form screenshot was not submitted; the Key Vault form used a fake masked value and was cancelled without saving. The Logs result shows stored telemetry counts, not evidence of recipient delivery or a new deployment.

The owner has deferred full deployment-plan, progress, and completion captures. The included sample images satisfy the agreed illustration scope; they do not claim a completed end-to-end deployment.

Editorial review

Three sequential passes completed on the latest PR:

1. Newcomer clarity: removed repeated instructions, defined EPP, kept the five-step order and provider-neutral main guide, and distinguished portal views from script input captures.
2. Consistency and accuracy: matched -ApplicationId and -TenantId to the portal fields, used the actual platform and Tenant scope prompt labels, corrected the input-screen caption, and explained that a plan preview can build the C# package locally before approval. Checked authentication, cache settings, and activation boundaries against current source.
3. Final rendered read-through: shortened long sentences, checked captions and numbered steps, and refreshed this description to remove outdated image counts and the old editorial-draft notice.

The existing README table-formatting edit is preserved. Current main is already an ancestor of this branch; no conflict resolution or base merge was needed.

Verification

• Rendered all 13 Markdown documents; checked 374 links/image references, including local targets and heading anchors. All 38 distinct external URLs returned HTTP 200.
• Parsed 14 PowerShell, 6 JSON, and 4 JavaScript examples without executing them. No Azure deployment or new live KQL run was performed during this review.
• Reviewed all 12 added screenshots and their captions: six in the README, three in monitoring, and three in detailed onboarding. All PNGs decode successfully and contain no ancillary metadata.
• Confirmed the main guide contains no named phone providers and keeps the approved illustration scope.
• git diff --check passes. Runtime and infrastructure code are unchanged.

Ready for review after the editorial checks. This does not authorize merging or claim end-to-end deployment or recipient delivery.