SEO: internal blog links from service sections, fix Cache-Control header

- Cache-Control: public, max-age=3600 (was private no-cache) for better CDN caching
- Document & Data Extraction card: links to PDF extraction and due diligence articles
- Research Automation card: links to research automation and cost of manual work articles
- Custom AI Agents card: links to what-is-an-ai-agent and build-vs-buy articles
- Use case cards: Legal Due Diligence, Consultancy Research, Document Review each
  now link to corresponding blog article instead of /quote

index.php

@@ -7,7 +7,7 @@ ini_set('session.cookie_secure', '1');
 session_start();
 
 // Allow private caching with revalidation (CSRF token requires session)
-header("Cache-Control: private, no-cache, must-revalidate");
+header("Cache-Control: public, max-age=3600, stale-while-revalidate=86400");
 if (!isset($_SESSION['csrf_token'])) {
     $_SESSION['csrf_token'] = bin2hex(random_bytes(32));
 }
@@ -567,6 +567,10 @@ $twitter_card_image = "https://ukaiautomation.co.uk/assets/images/ukaiautomation
                         <li>Bulk PDF processing pipelines</li>
                         <li>GDPR-compliant handling throughout</li>
                     </ul>
+                    <p style="margin-top:16px;font-size:0.9rem;">
+                        <a href="/blog/articles/document-extraction-pdf-to-database" style="color:#4f46e5;text-decoration:none;margin-right:16px;">PDF to database extraction &rarr;</a>
+                        <a href="/blog/articles/due-diligence-automation-law-firms" style="color:#4f46e5;text-decoration:none;">Due diligence automation &rarr;</a>
+                    </p>
                 </div>
 
                 <div class="service-card animate-on-scroll" style="--animation-delay: 0.2s;">
@@ -582,6 +586,10 @@ $twitter_card_image = "https://ukaiautomation.co.uk/assets/images/ukaiautomation
                         <li>Automated research reports</li>
                         <li>Custom alert systems</li>
                     </ul>
+                    <p style="margin-top:16px;font-size:0.9rem;">
+                        <a href="/blog/articles/research-automation-management-consultancy" style="color:#4f46e5;text-decoration:none;margin-right:16px;">Research automation for consultancies &rarr;</a>
+                        <a href="/blog/articles/cost-of-manual-data-work-professional-services" style="color:#4f46e5;text-decoration:none;">Cost of manual data work &rarr;</a>
+                    </p>
                 </div>
 
                 <div class="service-card animate-on-scroll" style="--animation-delay: 0.3s;">
@@ -612,6 +620,10 @@ $twitter_card_image = "https://ukaiautomation.co.uk/assets/images/ukaiautomation
                         <li>Workflow automation with human-in-the-loop oversight</li>
                         <li>Integration with your existing tools and systems</li>
                     </ul>
+                    <p style="margin-top:16px;font-size:0.9rem;">
+                        <a href="/blog/articles/what-is-an-ai-agent-professional-services" style="color:#4f46e5;text-decoration:none;margin-right:16px;">What is an AI agent? &rarr;</a>
+                        <a href="/blog/articles/build-vs-buy-ai-automation-professional-services" style="color:#4f46e5;text-decoration:none;">Build vs buy guide &rarr;</a>
+                    </p>
                 </div>
             </div>
         </div>
@@ -656,17 +668,17 @@ $twitter_card_image = "https://ukaiautomation.co.uk/assets/images/ukaiautomation
                     <div style="text-align: center; padding: 20px; background: #f8f9fa; border-radius: 12px;">
                         <h4 style="color: #4f46e5; margin-bottom: 15px;">⚖️ Legal Due Diligence</h4>
                         <p style="color: #666; margin: 0;">Automate the extraction and summarisation of data from contracts, filings, and company documents during due diligence.</p>
-                        <a href="/quote" style="color: #4f46e5; text-decoration: none; font-weight: 500;">Get a Quote →</a>
+                        <a href="/blog/articles/due-diligence-automation-law-firms" style="color: #4f46e5; text-decoration: none; font-weight: 500;">How it works →</a>
                     </div>
                     <div style="text-align: center; padding: 20px; background: #f8f9fa; border-radius: 12px;">
                         <h4 style="color: #4f46e5; margin-bottom: 15px;">📊 Consultancy Research</h4>
                         <p style="color: #666; margin: 0;">Replace manual research hours with automated monitoring of markets, competitors, and regulatory changes.</p>
-                        <a href="/quote" style="color: #4f46e5; text-decoration: none; font-weight: 500;">Get a Quote →</a>
+                        <a href="/blog/articles/research-automation-management-consultancy" style="color: #4f46e5; text-decoration: none; font-weight: 500;">How it works →</a>
                     </div>
                     <div style="text-align: center; padding: 20px; background: #f8f9fa; border-radius: 12px;">
                         <h4 style="color: #4f46e5; margin-bottom: 15px;">📋 Document Review</h4>
                         <p style="color: #666; margin: 0;">AI-powered extraction and summarisation of contracts, NDAs, and legal documents — replacing the first pass of manual review.</p>
-                        <a href="/quote" style="color: #4f46e5; text-decoration: none; font-weight: 500;">Get a Quote →</a>
+                        <a href="/blog/articles/contract-review-automation-law-firms" style="color: #4f46e5; text-decoration: none; font-weight: 500;">How it works →</a>
                     </div>
                     <div style="text-align: center; padding: 20px; background: #f8f9fa; border-radius: 12px;">
                         <h4 style="color: #4f46e5; margin-bottom: 15px;">📈 Client Reporting</h4>