feat(graph): add Federation Graph page and enhance coverage

Adds a new Federation Graph page to display subgraphs and their 
schemas. Implements loading state and error handling. Enhances 
coverage reporting by including 'lcov' format for better insights 
into test coverage metrics.

app/pages/schemas/[id].vue

@@ -82,6 +82,7 @@
               prepend-icon="mdi-graph"
               variant="outlined"
               color="primary"
+              @click="viewFederationGraph"
             >
               View Federation Graph
             </v-btn>
@@ -159,6 +160,11 @@ const copyToClipboard = async () => {
   }
 }
 
+const viewFederationGraph = () => {
+  if (!schema.value?.ref) return
+  navigateTo(`/graph/${schema.value.ref}`)
+}
+
 // TODO: Fetch actual data from the GraphQL API
 onMounted(() => {
   // Mock data for now