fix(network-maps): address design critique — harden, normalize, clarify, polish

- Archive: two-step inline confirm in card dropdown menu
- Delete Device/Edge: two-step inline confirm in PropertiesPanel footer
- Context menu Delete: floating confirm bar instead of immediate deletion
- AI Generate New: two-step confirm when replacing existing diagram nodes
- DiagramHeader: show 'Unsaved changes' in amber when isDirty and not saving
- deviceRegistry: SECURITY_COLOR #f97316 → #f87171 (deprecated ember orange removed)
- CanvasEmptyPrompt: remove backdrop-blur (design system violation)
- CanvasEmptyPrompt: remove redundant 'Skip AI' bottom button (duplicate of Build manually card)
- CanvasEmptyPrompt: rounded-xl/rounded-2xl → rounded-lg, border-2 → border
- Topology bar: h-1 → h-2 + native tooltip with category breakdown
- AIAssistPanel: replace pulse-dot loading with spinner (consistent with rest of feature)
- ContextMenu: add shadow-lg (consistent with other dropdowns)
- DeviceNode tooltip: Position.Bottom → Position.Top (avoids canvas-edge clipping)
- CanvasEmptyPrompt: raise ⌘↵ hint from /50 opacity to full text-muted-foreground

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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

@@ -57,7 +57,7 @@ function DeviceNodeComponent({ data }: NodeProps) {
           </BaseNode>
         </NodeTooltipTrigger>
         {hasTooltipContent && (
-          <NodeTooltipContent position={Position.Bottom}>
+          <NodeTooltipContent position={Position.Top}>
             <div className="flex flex-col gap-1 min-w-[140px]">
               <TooltipRow label="Host" value={props.hostname} />
               <TooltipRow label="IP" value={props.ip} />