docs: DNS registration guide for public site

[tuxerrante]

Summary

Adds docs/DNS_REGISTRATION.md to make issue #91 actionable: naming criteria, candidate shortlist (including ideas from the issue), a recommended default (sre-simulator.com first), decision log template, and registration/DNS/TLS checklist. Cross-links from docs/ARCHITECTURE.md.

Test plan

• make install (fresh worktree)
• make validate — pass (existing ESLint warnings in ChatMessage.tsx, unchanged)
• make test
• make test-integration

Fixes #91

Made with Cursor

[Copilot]

Pull request overview

Adds a new documentation guide to help the team choose and register a public DNS name for the SRE Simulator website, and links it from the architecture documentation so it’s discoverable.

Changes:

• Added docs/DNS_REGISTRATION.md with naming goals/criteria, candidate shortlist, recommended default, decision log template, and post-selection checklist.
• Cross-linked the new guide from docs/ARCHITECTURE.md and updated the docs tree to include it.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
docs/DNS_REGISTRATION.md	New actionable guide for selecting/recording/registering a public website domain and DNS/TLS steps.
docs/ARCHITECTURE.md	Adds a reference to the new DNS guide and updates the documented repo structure.

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[tuxerrante]

Domain/DNS rollout plan (deferred)

Keeping this noted here so we can execute later, after remaining infra/test fixes are completed.

• Decision for now: target sresimulator.com (cheaper and practical fallback).
• sre.io is currently unavailable at registrar lookup, so not proceeding with that name now.
• Defer domain purchase until current fix work is complete.

When ready to execute:

1. Buy sresimulator.com at the chosen registrar.
2. Ensure Azure DNS zone exists for sresimulator.com (and delegated nameservers if newly created).
3. Set Terraform DNS variables:
   • public_dns_zone_name = "sresimulator.com"
   • public_dns_resource_group_name = "<dns-rg>"
   • public_dns_record_name = "www"
   • optional public_dns_target override only if auto-derived target is not desired.
4. Run make tf-plan OWNER_ALIAS=<alias> + make tf-apply OWNER_ALIAS=<alias> CONFIRM_APPLY=<alias>.
5. Verify DNS in Azure (az network dns record-set cname show ...) and app reachability.
6. Keep canonical URL as https://www.sresimulator.com; configure apex (sresimulator.com) redirect to www.
7. TLS/certificates handled at ingress/hosting layer after DNS cutover.

This keeps DNS as Terraform-managed while avoiding premature registrar/domain churn.