feat: ws client & new backups frontend

[IMB11]

• Creates the new websocket client in the packages/api-client;
  • Uses mitt for event handling
  • Cross platform by design - no custom nuxt impl is needed.
  • Can support multiple server connections (although we probably wont use this for anything user facing)
  • Follows event bus structure
  • Root page connects, child pages/components can subscribe to events safely, as long as they unsubscribe on unmounted.

<script setup lang="ts">
const client = injectModrinthClient();

const unsubscribers = ref<(() => void)[]>([])

onMounted(() => {
    // safeConnect prevents a new connection if one already exists, impl details are irrelevant
    await client.ws.safeConnect(serverId);

    unsubscribers.value.push(
        // Just some examples, obv would be in subcomponents etc.                                                    
        client.ws.on(serverId, 'log', handleLog),
        client.ws.on(serverId, 'stats', handleStats),
        client.ws.on(serverId, 'power-state', handlePowerState),
        client.ws.on(serverId, 'uptime', handleUptime),
        client.ws.on(serverId, 'auth-expiring', handleAuthExpiring),
        client.ws.on(serverId, 'auth-incorrect', handleAuthExpiring),
        client.ws.on(serverId, 'auth-ok', () => {}), // no-op example                    
        client.ws.on(serverId, 'installation-result', handleInstallationResult),
    );
});

onUnmounted(() => {
    unsubscribers.value.forEach(func => func());
	client.ws.disconnect(serverId);
});
</script>

• Convert the legacy backups server module into api-client under ArchonBackupsV1Module
• Replace the old WS client in index.vue with the new one
  • Convert other WS usages (power, new-content, etc.) to new client design
• Implement new backups page design from Figma and move it to the new page system introduced in feat: start of cross platform page system #4731