feat(blog): remove Visual_Blueprint_Ref from header and improve AI thumbnail prompts

apps/web/src/components/blog/BlogPostHeader.tsx

@@ -58,11 +58,6 @@ export const BlogPostHeader: React.FC<BlogPostHeaderProps> = ({
                 />
                 <div className="absolute inset-0 bg-gradient-to-t from-slate-900/20 to-transparent mix-blend-multiply" />
               </div>
-
-              {/* Technical label */}
-              <div className="absolute top-4 right-4 px-3 py-1 bg-white/90 backdrop-blur-sm border border-slate-200 rounded text-[8px] font-mono text-slate-500 uppercase tracking-widest">
-                Visual_Blueprint_Ref: {slug?.substring(0, 8).toUpperCase()}
-              </div>
             </div>
           </Reveal>
         )}