Add supplied post images to two posts and to the blog overview cards

- blog/posts/odoo-19-to-20-invoice-migration-with-n8n-and-mcp.html: in-post image
  much.png + og:image
- blog/posts/track-the-oca-modules-you-actually-use.html: in-post image
  oca_module_status.png + og:image
- blog/index.json: optional "image" key on those two entries only (text splice)
- script.js: renderBlog() draws .blog-thumb only when the entry carries an image
- style.css: .blog-thumb rule
- sitemap.xml: lastmod 2026-10-24 for the invoice-migration post

Built by profile webmaster (run 20261024_094206_5c4f28, verified PROBLEMS: 0 /
node --check OK); committed by olchi after that run died on an OpenRouter 402.

sitemap.xml

@@ -20,7 +20,7 @@
   </url>
   <url>
     <loc>https://odoo4projects.com/blog/posts/odoo-19-to-20-invoice-migration-with-n8n-and-mcp.html</loc>
-    <lastmod>2026-10-23</lastmod>
+    <lastmod>2026-10-24</lastmod>
     <changefreq>monthly</changefreq>
     <priority>0.6</priority>
   </url>