[refactor] Improve workflow domain organization (#5584)

* [refactor] move workflow domain to its own folder

* [refactor] Fix workflow platform architecture organization

- Move workflow rendering functionality to renderer/thumbnail domain
- Rename ui folder to management for better semantic clarity
- Update all import paths to reflect proper domain boundaries
- Fix test imports to use new structure

Architecture improvements:
- rendering → renderer/thumbnail (belongs with other rendering logic)
- ui → management (better name for state management and UI integration)

This ensures proper separation of concerns and domain boundaries.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* [fix] Resolve circular dependency between nodeDefStore and subgraphStore

* [fix] Update browser test imports to use new workflow platform paths

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Co-authored-by: Claude <noreply@anthropic.com>

src/components/templates/TemplateWorkflowView.spec.ts

@@ -3,7 +3,7 @@ import { describe, expect, it, vi } from 'vitest'
 import { createI18n } from 'vue-i18n'
 
 import TemplateWorkflowView from '@/components/templates/TemplateWorkflowView.vue'
-import { TemplateInfo } from '@/types/workflowTemplateTypes'
+import { TemplateInfo } from '@/platform/workflow/templates/types/template'
 
 vi.mock('primevue/dataview', () => ({
   default: {