fix(rack-planner): resolve infinite re-render loop in ConnectionLayer and add null-safety for VLAN tooltips

client/src/components/rack/ModuleBlock.tsx

@@ -184,7 +184,7 @@ export function ModuleBlock({ module }: ModuleBlockProps) {
                       onClick={(e) => handlePortClick(e, port.id)}
                       aria-label={`Port ${port.portNumber}`}
                       title={`Port ${port.portNumber}${port.label ? ` · ${port.label}` : ''}${
-                        hasVlan ? ` (VLAN ${port.vlans.map((v) => v.vlan.vlanId).join(',')})` : ''
+                        hasVlan ? ` (VLAN ${port.vlans.map((v) => v.vlan?.vlanId).filter(Boolean).join(',')})` : ''
                       }\nShift+Click for settings`}
                       style={{ backgroundColor: vlanColor, borderColor: 'rgba(0,0,0,0.2)' }}
                       className={cn(