feat: real-time WebSocket metrics broadcaster and UI updates

- New metrics_broadcaster service (410 lines) — background broadcaster
  pushing CPU/RAM/disk/network stats to subscribed WebSocket clients
- WebSocket protocol extended: subscribe/unsubscribe channels,
  get_rrd/get_node_rrd requests with request_id
- main.py: metrics broadcaster started in lifespan, WS message dispatcher
- websocket_manager.py: subscription map support
- templates: dashboard, instance_detail, proxmox_server_detail,
  proxmox_vms, workspaces — real-time charts and UI updates
- auth.py, servers.py, settings.py: minor fixes

backend/app/api/proxmox/servers.py

@@ -33,9 +33,11 @@ def vms_page(request: Request, db: Session = Depends(get_db)):
     """Страница управления Proxmox серверами, VM и LXC"""
     from ...i18n import t
     lang = request.cookies.get("language", "en")
-    
+
+    # All servers are needed for cluster modals (admin operations).
+    # The main servers table is rendered dynamically via JS with workspace filtering.
     proxmox_servers = db.query(ProxmoxServer).all()
-    
+
     context = {
         "request": request,
         "proxmox_servers": proxmox_servers,