feat: rename service-card "Demo" buttons to "Live Use Case"

Owner flagged these as reading like unfinished-demo links when every one
of them actually points to a real, running product (GT, Snehalata, EA
dashboard, etc.) — relabeling makes that honest.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/projects.jsx

@@ -175,7 +175,7 @@ const ProjectCard = ({ p }) => {
                 fontWeight: 500,
                 textDecoration: "none",
                 cursor: "pointer",
-              }}>Demo <Icons.ArrowUpRight size={12} /></a>
+              }}>Live Use Case <Icons.ArrowUpRight size={12} /></a>
             )}
           </div>
         </div>