fix: address code review findings for React Flow UI integration

- Use screenToFlowPosition() for drop coordinates (fixes zoom/pan bug)
- Remove duplicate selection border from DeviceNode (BaseNode handles it)
- Add w-full to GroupNode for proper container sizing
- Remove unused 'selected' destructuring from DeviceNode

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/network/nodes/DeviceNode.tsx

@@ -25,7 +25,7 @@ function TooltipRow({ label, value }: { label: string; value: string | null | un
   )
 }
 
-function DeviceNodeComponent({ data, selected }: NodeProps) {
+function DeviceNodeComponent({ data }: NodeProps) {
   const nodeData = data as unknown as DeviceNodeData
   const { icon: Icon, color } = getDeviceRenderConfig(nodeData.deviceType, nodeData.category)
   const status = (nodeData.properties?.status || 'unknown') as NodeStatus
@@ -38,7 +38,7 @@ function DeviceNodeComponent({ data, selected }: NodeProps) {
     <NodeStatusIndicator status={status}>
       <NodeTooltip>
         <NodeTooltipTrigger>
-          <BaseNode className={`min-w-[120px] group ${selected ? 'border-accent' : ''}`}>
+          <BaseNode className="min-w-[120px] group">
             <BaseNodeHeader className="flex-col gap-1 items-center py-3 px-4">
               <Icon size={28} style={{ color }} />
               <BaseNodeHeaderTitle className="text-center text-xs">

frontend/src/components/network/ui/labeled-group-node.tsx

@@ -45,7 +45,7 @@ export function GroupNode({ data, selected }: NodeProps) {
   return (
     <BaseNode
       className={cn(
-        'h-full min-h-[200px] min-w-[300px] overflow-hidden rounded-lg bg-elevated/30 border-default/50',
+        'h-full w-full min-h-[200px] min-w-[300px] overflow-hidden rounded-lg bg-elevated/30 border-default/50',
         selected && 'border-accent',
       )}
     >