feat: use get_featured_image partial consistently for og:image and JSON-LD (#3311)

site_head.html, jsonld/article.html, jsonld/qapage.html, and
jsonld/event.html hardcode `(.Resources.ByType "image").GetMatch
"*featured*"` to find featured images. This ignores custom filenames
set via `.Params.image.filename` in front matter, causing og:image
and JSON-LD image to fall back to the site icon.

Replace the hardcoded pattern with the `get_featured_image` partial
(already used by jsonld/webpage.html), which properly searches for:
1. Files matching `*featured*` in the page directory
2. Custom filename from `.Params.image.filename` in the page directory
3. Custom filename in `assets/media/` directory

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

modules/blox/layouts/_partials/jsonld/article.html

@@ -1,6 +1,6 @@
 {{- $page := .page }}
 {{ $summary := .summary }}
-{{ $featured_image := ($page.Resources.ByType "image").GetMatch "*featured*" }}
+{{ $featured_image := partial "functions/get_featured_image" $page }}
 
 {{/* Get schema type. */}}
 {{ $schema := "Article" }}

modules/blox/layouts/_partials/jsonld/event.html

@@ -1,6 +1,6 @@
 {{ $page := .page }}
 {{ $summary := .summary }}
-{{ $featured_image := ($page.Resources.ByType "image").GetMatch "*featured*" }}
+{{ $featured_image := partial "functions/get_featured_image" $page }}
 {{ $author := partial "functions/get_author_name" $page }}
 
 <script type="application/ld+json">

modules/blox/layouts/_partials/jsonld/qapage.html

@@ -1,6 +1,6 @@
 {{- $page := .page }}
 {{ $summary := .summary }}
-{{ $featured_image := ($page.Resources.ByType "image").GetMatch "*featured*" }}
+{{ $featured_image := partial "functions/get_featured_image" $page }}
 
 {{/* Get author and publisher info */}}
 {{ $author := partial "functions/get_author_name" $page }}

modules/blox/layouts/_partials/site_head.html

@@ -116,7 +116,7 @@
 
   {{/* Get page image for sharing. */}}
   {{ $sharing_image := resources.GetMatch (path.Join "media" "sharing.*") }}
-  {{ $featured_image := (.Resources.ByType "image").GetMatch "*featured*" }}
+  {{ $featured_image := partial "functions/get_featured_image" . }}
 {{ $avatar_image := (.Resources.ByType "image").GetMatch "avatar*" }}
   {{ $has_logo := fileExists "assets/media/logo.png" | or (fileExists "assets/media/logo.svg") }}
   {{ $og_image := "" }}