Add force update functionality for Ghost posts

- Add manual CI trigger 'force-update-ghost' for updating all posts
- Support FORCE_UPDATE environment variable in Rust code
- Implement post update logic via Ghost API PUT requests
- Add get_existing_post_id() function to find existing posts
- Update README with usage instructions
- Enhanced validation script to test new functionality

Usage:
- Normal: Only syncs new posts (default behavior)
- Force: FORCE_UPDATE=true updates ALL posts including existing ones

validate-ghost-extraction.sh

@@ -49,6 +49,22 @@ else
     exit 1
 fi
 
+# Check if force update functionality is available
+if grep -q "FORCE_UPDATE" ghost-upload/src/main.rs; then
+    echo "✅ Force update functionality found"
+else
+    echo "❌ Force update functionality not found"
+    exit 1
+fi
+
+# Check if manual CI job is configured
+if grep -q "force-update-ghost" ghost-upload/.gitlab-ci.yml; then
+    echo "✅ Manual force update CI job found"
+else
+    echo "❌ Manual force update CI job not found"
+    exit 1
+fi
+
 # Verify Rust code compiles
 echo "🛠️  Building Rust code..."
 cd ghost-upload
@@ -67,5 +83,7 @@ echo "   • Quarto profiles for dual-output rendering"
 echo "   • Ghost-optimized CSS styling"
 echo "   • GitLab CI builds both main site and ghost-content"
 echo "   • Rust extracts HTML content instead of using iframes"
+echo "   • Force update mode to refresh existing posts"
+echo "   • Manual CI trigger for content updates"
 echo ""
 echo "🚀 Ready for testing in CI/CD pipeline!"