Add CNAME file for GitHub Pages custom domain (openkline.tech)

[rekurt]

Why

The GitHub Pages custom domain health check is failing for openkline.tech:

DNS check unsuccessful — Domain does not resolve to the GitHub Pages server (NotServedByPagesError).

I checked the live DNS and most of it is actually correct, so the failure comes down to two things — one of which is fixed here.

Live DNS state

Record	Result	Status
openkline.tech A	185.199.108–111.153 (the 4 GitHub Pages IPs)	✅ correct
openkline.tech AAAA	none	❌ missing
www.openkline.tech	CNAME → rekurt.github.io	✅ correct
repo CNAME file	did not exist	❌ → fixed in this PR

What this PR does

Adds a root CNAME file containing openkline.tech. GitHub Pages requires this file in the publishing source to claim and serve the custom domain; without it the domain is not served by Pages.

Important

This file only takes effect if it lands on the branch/source that Pages publishes from (e.g. master root). Merge this into that branch.

Still required outside the repo (DNS registrar)

Add the four apex AAAA records so the apex matches GitHub's current health-check expectations:

openkline.tech.  AAAA  2606:50c0:8000::153
openkline.tech.  AAAA  2606:50c0:8001::153
openkline.tech.  AAAA  2606:50c0:8002::153
openkline.tech.  AAAA  2606:50c0:8003::153

Then in Settings → Pages, re-enter the custom domain (or click Check again) to force GitHub to re-run the now-stale health check.

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