feat: Integrate Relay Hub for centralized Nostr connection management

- Introduce a new composable, useRelayHub, to manage all Nostr WebSocket connections, enhancing connection stability and performance.
- Update existing components and composables to utilize the Relay Hub for connecting, publishing events, and subscribing to updates, streamlining the overall architecture.
- Add a RelayHubStatus component to display connection status and health metrics, improving user feedback on the connection state.
- Implement a RelayHubDemo page to showcase the functionality of the Relay Hub, including connection tests and subscription management.
- Ensure proper error handling and logging throughout the integration process to facilitate debugging and user experience.

src/components/layout/Navbar.vue

@@ -33,6 +33,7 @@ const navigation = computed<NavigationItem[]>(() => [
   { name: t('nav.events'), href: '/events' },
   { name: t('nav.market'), href: '/market' },
   { name: t('nav.chat'), href: '/chat' },
+  { name: 'Relay Hub', href: '/relay-hub-demo' },
 ])
 
 // Compute total wallet balance
@@ -149,6 +150,10 @@ const handleLogout = async () => {
                 <Ticket class="h-4 w-4" />
                 My Tickets
               </DropdownMenuItem>
+              <DropdownMenuItem @click="() => router.push('/relay-hub-demo')" class="gap-2">
+                <MessageSquare class="h-4 w-4" />
+                Relay Hub Demo
+              </DropdownMenuItem>
               <DropdownMenuSeparator />
               <DropdownMenuItem @click="handleLogout" class="gap-2 text-destructive">
                 <LogOut class="h-4 w-4" />
@@ -230,6 +235,11 @@ const handleLogout = async () => {
                 <Ticket class="h-4 w-4" />
                 My Tickets
               </Button>
+              <Button variant="ghost" size="sm" @click="() => router.push('/relay-hub-demo')"
+                class="w-full justify-start gap-2">
+                <MessageSquare class="h-4 w-4" />
+                Relay Hub Demo
+              </Button>
               <Button variant="ghost" size="sm" @click="handleLogout"
                 class="w-full justify-start gap-2 text-destructive">
                 <LogOut class="h-4 w-4" />