[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/topbar/WorkflowOverflowMenu.vue

@@ -23,8 +23,8 @@ import Button from 'primevue/button'
 import Menu from 'primevue/menu'
 import { computed, ref } from 'vue'
 
-import { useWorkflowService } from '@/services/workflowService'
-import type { ComfyWorkflow } from '@/stores/workflowStore'
+import { useWorkflowService } from '@/platform/workflow/core/services/workflowService'
+import type { ComfyWorkflow } from '@/platform/workflow/management/stores/workflowStore'
 
 const props = defineProps<{
   workflows: ComfyWorkflow[]