docs: drop the redundant README H1, centre the intro

The horizontal logo already carries the wordmark, so "# Cairn OBS"
directly beneath it repeated the same words twice in the first inch of
the page. Removed, and the tagline and licence line centred under the
logo so the header reads as one block.

The bold and the link are written as <strong>/<a> rather than markdown:
GitHub does not process markdown inside a raw HTML block, so **...** and
[...](...) would have rendered as literal asterisks and brackets.

Nothing linked to the removed heading, and the #licensing anchor it
referenced comes from `## Licensing`, which is untouched.

README.md

@@ -7,14 +7,16 @@
   </picture>
 </p>
 
-# Cairn OBS
+<p align="center">
+  Open-core, Kubernetes-native log aggregation and observability.<br>
+  Built to match Splunk on capability while winning on cost-per-GB,<br>
+  with honest multi-tenant RBAC and a modern language stack.
+</p>
 
-Open-core, Kubernetes-native log aggregation and observability. Built to match
-Splunk on capability while winning on cost-per-GB, with honest multi-tenant
-RBAC and a modern language stack.
-
-Licensed **AGPLv3 in its entirety** — including `enterprise/`. See
-[Licensing](#licensing).
+<p align="center">
+  Licensed <strong>AGPLv3 in its entirety</strong> — including
+  <code>enterprise/</code>. See <a href="#licensing">Licensing</a>.
+</p>
 
 ## What it does