fix(seo): repair the 10 blog canonicals, sitemap.xml, blog/index.json and llms.txt

From seo/out/site-seo-ai-search-audit-2026-10-27.md (§6 items 1, 2, 3a, 5).

- canonical: 10 blog posts declared https://odooprojects.com/... — a live parked
  third-party domain — as their canonical. Now self-referencing on
  https://odoo4projects.com/blog/posts/<slug>.html (1 line each, nothing else).
- sitemap.xml: 27 -> 33 URLs. Added the 6 live pages that were missing
  (support.html, legal.html, community-vs-enterprise-cost, 6-tips,
  odoocommunity-agents, odoo-20-is-live); corrected 13 lastmod values to the
  real last content commit (homepage was 4 months stale); /de/ and /es/
  priority 1.0 -> 0.7 so a translation does not outrank its original.
- blog/index.json: 7 -> 15 posts. The 8 orphan posts are now listed, so every
  post is reachable from the homepage grid.
- llms.txt: removed the link to /blog/ (that URL returns 403) and added a
  "## Blog posts" section listing all 15 posts with date and summary.

Not changed on purpose: FAQPage on support.html, the homepage "price": ">950.00",
the bootcamp start-date conflict, and the blog post chrome (15 files).

blog/posts/howto-custom-module.html

@@ -13,7 +13,7 @@
         />
         <link
             rel="canonical"
-            href="https://odooprojects.com/blog/posts/howto-custom-module.html"
+            href="https://odoo4projects.com/blog/posts/howto-custom-module.html"
         />
         <meta
             property="og:title"