fix: use get_featured_image partial consistently for og:image and JSON-LD

[chezou]

🚀 What type of change is this?

• 🐛 Bug fix (A non-breaking change that fixes an issue)
• ✨ New feature (A non-breaking change that adds functionality)
• 💅 Style change (A change that only affects formatting, visuals, or styling)
• 📚 Documentation update (Changes to documentation only)
• 🧹 Refactor or chore (A code change that neither fixes a bug nor adds a feature)
• 💥 Breaking change (A fix or feature that would cause existing functionality to not work as expected)

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🎯 What is the purpose of this change?

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

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📸 Screenshots or Screencast (if applicable)

Before:

After:

(URL in the post: https://chezo.uno/post/2026-03-28-montreal%E3%81%AB10%E5%B9%B4%E4%BB%A5%E4%B8%8A%E3%81%B5%E3%82%8A%E3%81%AB%E8%A1%8C%E3%81%A3%E3%81%9F/ )

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ℹ️ Documentation Check

• No, this change does not require a documentation update.
• Yes, I have updated the documentation accordingly (or will in a follow-up PR).

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[netlify]

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[github-actions]

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[chezou]

Per Github Copilot with GPT-5.4, the CI failures are unrelated with my change.

Here is the brief analysis by GPT-5.4:
This CI failure looks unrelated to the featured-image change in this PR. The failing matrix job is in templates/dev-portfolio, where content/_index.md references devicon/amazonwebservices-wordmark, which appears missing and becomes fatal under --panicOnWarning.