Add an RSS feed for the blog

hugo.yaml pins every page kind's outputs to ["HTML"] only, which
disables Hugo's built-in feed generation site-wide. Scoped RSS back on
for just the blog section (content/blog/_index.md's own `outputs:`
front matter overrides the site default for that page) rather than
flipping it on globally, so the resources catalog doesn't grow a feed
per category too.

- /blog/index.xml — standard RSS 2.0, one <item> per post, needed to
  submit the blog to Planet for the MySQL Community and similar
  aggregators.
- head.html now emits a <link rel="alternate" type="application/rss+xml">
  wherever a page actually has one (via .AlternativeOutputFormats), so
  it only shows up on /blog/ — home keeps its own JSON alternate link
  for the search index, unaffected.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: Mazizova

content/blog/_index.md

@@ -1,4 +1,7 @@
 ---
 title: "Blog"
 description: "News, announcements, and updates from OurSQL Foundation."
+outputs:
+- HTML
+- RSS
 ---

layouts/partials/head.html

@@ -16,6 +16,11 @@
 {{/* ── Robots ── */}}
 <meta name="robots" content="index, follow">
 
+{{/* ── Feed auto-discovery (only present on pages that actually have one, e.g. /blog/) ── */}}
+{{ range .AlternativeOutputFormats }}
+<link rel="alternate" type="{{ .MediaType.Type }}" href="{{ .Permalink }}" title="{{ $.Site.Title }} — {{ $.Title }}">
+{{ end }}
+
 {{/* ── OG image: front matter → default social cover ── */}}
 {{ $ogImage := "" }}
 {{ if .Params.image }}