[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/components/dialog/content/manager/skeleton/PackCardGridSkeleton.test.ts

@@ -1,80 +0,0 @@
-import type { VueWrapper } from '@vue/test-utils'
-import { mount } from '@vue/test-utils'
-import { createPinia } from 'pinia'
-import PrimeVue from 'primevue/config'
-import { describe, expect, it } from 'vitest'
-import { nextTick } from 'vue'
-import { createI18n } from 'vue-i18n'
-
-import enMessages from '@/locales/en/main.json' with { type: 'json' }
-
-import GridSkeleton from './GridSkeleton.vue'
-import PackCardSkeleton from './PackCardSkeleton.vue'
-
-describe('GridSkeleton', () => {
-  const mountComponent = ({
-    props = {}
-  }: Record<string, any> = {}): VueWrapper => {
-    const i18n = createI18n({
-      legacy: false,
-      locale: 'en',
-      messages: { en: enMessages }
-    })
-
-    return mount(GridSkeleton, {
-      props: {
-        gridStyle: {
-          display: 'grid',
-          gridTemplateColumns: 'repeat(auto-fill, minmax(19rem, 1fr))',
-          padding: '0.5rem',
-          gap: '1.5rem'
-        },
-        ...props
-      },
-      global: {
-        plugins: [PrimeVue, createPinia(), i18n],
-        stubs: {
-          PackCardSkeleton: true
-        }
-      }
-    })
-  }
-
-  it('renders with default props', () => {
-    const wrapper = mountComponent()
-    expect(wrapper.exists()).toBe(true)
-  })
-
-  it('applies the provided grid style', () => {
-    const customGridStyle = {
-      display: 'grid',
-      gridTemplateColumns: 'repeat(auto-fill, minmax(15rem, 1fr))',
-      padding: '1rem',
-      gap: '1rem'
-    }
-
-    const wrapper = mountComponent({
-      props: { gridStyle: customGridStyle }
-    })
-
-    const gridElement = wrapper.element
-    expect(gridElement.style.display).toBe('grid')
-    expect(gridElement.style.gridTemplateColumns).toBe(
-      'repeat(auto-fill, minmax(15rem, 1fr))'
-    )
-    expect(gridElement.style.padding).toBe('1rem')
-    expect(gridElement.style.gap).toBe('1rem')
-  })
-
-  it('renders the specified number of skeleton cards', async () => {
-    const cardCount = 5
-    const wrapper = mountComponent({
-      props: { skeletonCardCount: cardCount }
-    })
-
-    await nextTick()
-
-    const skeletonCards = wrapper.findAllComponents(PackCardSkeleton)
-    expect(skeletonCards.length).toBe(5)
-  })
-})