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/deviceRegistry.ts

@@ -20,7 +20,7 @@ export interface DeviceRenderConfig {
 // Cloud    (cyan)   — external/internet-connected
 // Infra    (steel)  — physical/passive hardware
 export const NETWORK_COLOR  = '#60a5fa'
-export const SECURITY_COLOR = '#f97316'
+export const SECURITY_COLOR = '#f87171'
 export const COMPUTE_COLOR  = '#34d399'
 export const ENDPOINT_COLOR = '#fbbf24'
 export const STORAGE_COLOR  = '#a78bfa'