feat: add Docker node type, group rect border style, and categorized node type selector

- Fix DockerNode default icon: use Anchor instead of Package
- Add border_style option to Group Rectangle (solid/dashed/dotted/double/none)
- Group node type selector by category (Hardware, Virtualization, IoT, Generic)
- Add tests for border style feature

frontend/src/utils/__tests__/themes.test.ts

@@ -4,7 +4,7 @@ import type { NodeType, EdgeType, NodeStatus } from '@/types'
 
 const NODE_TYPES: NodeType[] = [
   'isp', 'router', 'switch', 'server', 'proxmox', 'vm', 'lxc',
-  'nas', 'iot', 'ap', 'camera', 'printer', 'computer', 'cpl', 'generic', 'groupRect',
+  'nas', 'iot', 'ap', 'camera', 'printer', 'computer', 'cpl', 'docker', 'generic', 'groupRect',
 ]
 const EDGE_TYPES: EdgeType[] = ['ethernet', 'wifi', 'iot', 'vlan', 'virtual', 'cluster']
 const STATUS_TYPES: NodeStatus[] = ['online', 'offline', 'pending', 'unknown']
@@ -84,6 +84,7 @@ describe('THEMES', () => {
     expect(d.nodeAccents.server.border).toBe('#a855f7')
     expect(d.nodeAccents.isp.border).toBe('#00d4ff')
     expect(d.nodeAccents.proxmox.border).toBe('#ff6e00')
+    expect(d.nodeAccents.docker.border).toBe('#2496ED')
     expect(d.nodeCardBackground).toBe('#21262d')
     expect(d.nodeIconBackground).toBe('#161b22')
     expect(d.canvasBackground).toBe('#0d1117')