SEO fixes: orphan pages, schema cleanup, clean URLs, llms-full.txt

- Add 32 missing articles to blog page 2 with working pagination
- Strip .php extensions from all blog article links (blog/index.php, article-footer.php)
- Remove unverified aggregateRating from Organization schema
- Remove empty telephone fields from Organization schema
- Fix broken tel: link in homepage contact section (+44 1692 689150)
- Update footer Twitter link to x.com
- Create llms-full.txt for AI crawler indexing

includes/footer.php

@@ -96,7 +96,7 @@
                 </div>
                 <div class="social-links">
                     <a href="https://linkedin.com/company/uk-data-services" aria-label="LinkedIn" target="_blank" rel="noopener noreferrer"><img src="/assets/images/icon-linkedin.svg" alt="LinkedIn" loading="lazy"></a>
-                    <a href="https://twitter.com/ukdataservices" aria-label="Twitter" target="_blank" rel="noopener noreferrer"><img src="/assets/images/icon-twitter.svg" alt="Twitter" loading="lazy"></a>
+                    <a href="https://x.com/ukdataservices" aria-label="Twitter" target="_blank" rel="noopener noreferrer"><img src="/assets/images/icon-twitter.svg" alt="Twitter" loading="lazy"></a>
                 </div>
             </div>
         </div>