[refactor] Migrate manager code to DDD structure (#5662)

## Summary

Reorganized custom nodes manager functionality from scattered technical
layers into a cohesive domain-focused module following [domain-driven
design](https://en.wikipedia.org/wiki/Domain-driven_design) principles.

## Changes

- **What**: Migrated all manager code from technical layers
(`src/components/`, `src/stores/`, etc.) to unified domain structure at
`src/workbench/extensions/manager/`
- **Breaking**: Import paths changed for all manager-related modules
(40+ files updated)

## Review Focus

Verify all import path updates are correct and no circular dependencies
introduced. Check that [Vue 3 composition
API](https://vuejs.org/guide/reusability/composables.html) patterns
remain consistent across relocated composables.


┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5662-refactor-Migrate-manager-code-to-DDD-structure-2736d73d3650812c87faf6ed0fffb196)
by [Unito](https://www.unito.io)

src/composables/nodePack/usePacksSelection.ts

@@ -1,7 +1,7 @@
 import { type Ref, computed } from 'vue'
 
-import { useComfyManagerStore } from '@/stores/comfyManagerStore'
 import type { components } from '@/types/comfyRegistryTypes'
+import { useComfyManagerStore } from '@/workbench/extensions/manager/stores/comfyManagerStore'
 
 type NodePack = components['schemas']['Node']