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>
