refactor: update button colors in CallToAction and Hero components for improved contrast

- Changed link button color from cyan to white in agents, home, and network CallToAction components
- Updated network Hero secondary button from dark to gray outline variant

src/pages/network/CallToAction.tsx

@@ -65,7 +65,7 @@ Use the network to link environments, deploy workloads, or host nodes to strengt
                 Deploy in Cloud
               </Button>
 
-              <Button to="/nodes" variant="link" color="cyan">
+              <Button to="/nodes" variant="link" color="white">
                 Host a Node &rarr;
               </Button>
             </div>